diff --git a/README.md b/README.md
index 50b3bdb..6b212f4 100644
--- a/README.md
+++ b/README.md
@@ -11,7 +11,7 @@ This package provides Python implementations of the following
 [ProseMirror](https://prosemirror.net/) packages:
 
 - [`prosemirror-model`](https://github.com/ProseMirror/prosemirror-model) version 1.18.1
-- [`prosemirror-transform`](https://github.com/ProseMirror/prosemirror-transform) version 1.6.0
+- [`prosemirror-transform`](https://github.com/ProseMirror/prosemirror-transform) version 1.7.1
 - [`prosemirror-test-builder`](https://github.com/ProseMirror/prosemirror-test-builder)
 - [`prosemirror-schema-basic`](https://github.com/ProseMirror/prosemirror-schema-basic) version 1.1.2
 - [`prosemirror-schema-list`](https://github.com/ProseMirror/prosemirror-schema-list)
@@ -87,4 +87,4 @@ assert tr.doc.to_json() == {
         }]
     }]
 }
-```
\ No newline at end of file
+```
diff --git a/poetry.lock b/poetry.lock
index 62adeaa..9978472 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.4.2 and should not be changed by hand.
 
 [[package]]
 name = "attrs"
@@ -182,14 +182,14 @@ colorama = {version = "*", markers = "platform_system == \"Windows\""}
 
 [[package]]
 name = "codecov"
-version = "2.1.12"
+version = "2.1.13"
 description = "Hosted coverage reports for GitHub, Bitbucket and Gitlab"
 category = "dev"
 optional = false
 python-versions = ">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*"
 files = [
-    {file = "codecov-2.1.12-py2.py3-none-any.whl", hash = "sha256:585dc217dc3d8185198ceb402f85d5cb5dbfa0c5f350a5abcdf9e347776a5b47"},
-    {file = "codecov-2.1.12.tar.gz", hash = "sha256:a0da46bb5025426da895af90938def8ee12d37fcbcbbbc15b6dc64cf7ebc51c1"},
+    {file = "codecov-2.1.13-py2.py3-none-any.whl", hash = "sha256:c2ca5e51bba9ebb43644c43d0690148a55086f7f5e6fd36170858fa4206744d5"},
+    {file = "codecov-2.1.13.tar.gz", hash = "sha256:2362b685633caeaf45b9951a9b76ce359cd3581dd515b430c6c3f5dfb4d92a8c"},
 ]
 
 [package.dependencies]
@@ -725,4 +725,4 @@ socks = ["PySocks (>=1.5.6,!=1.5.7,<2.0)"]
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.8.1,<4"
-content-hash = "2d986f3721f23927f09587eee9ed4c3efdba93943a2c545e380418077f259b8a"
+content-hash = "f5c6e0791a18839add2821b9e38fa4c3c25980701713919c7038348312791f43"
diff --git a/prosemirror/transform/mark_step.py b/prosemirror/transform/mark_step.py
index eb538e2..c77afb3 100644
--- a/prosemirror/transform/mark_step.py
+++ b/prosemirror/transform/mark_step.py
@@ -153,3 +153,112 @@ def from_json(schema, json_data):
 
 
 Step.json_id("removeMark", RemoveMarkStep)
+
+
+class AddNodeMarkStep(Step):
+    def __init__(self, pos, mark):
+        super().__init__()
+        self.pos = pos
+        self.mark = mark
+
+    def apply(self, doc):
+        node = doc.node_at(self.pos)
+        if not node:
+            return StepResult.fail("No node at mark step's position")
+        updated = node.type.create(node.attrs, None, self.mark.add_to_set(node.marks))
+        return StepResult.from_replace(
+            doc,
+            self.pos,
+            self.pos + 1,
+            Slice(Fragment.from_(updated), 0, 0 if node.is_leaf else 1),
+        )
+
+    def invert(self, doc):
+        node = doc.node_at(self.pos)
+        if node:
+            new_set = self.mark.add_to_set(node.marks)
+            if len(new_set) == len(node.marks):
+                for i in range(len(node.marks)):
+                    if not node.marks[i].is_in_set(new_set):
+                        return AddNodeMarkStep(self.pos, node.marks[i])
+                return AddNodeMarkStep(self.pos, self.mark)
+        return RemoveNodeMarkStep(self.pos, self.mark)
+
+    def map(self, mapping):
+        pos = mapping.map_result(self.pos, 1)
+        return None if pos.deleted_after else AddNodeMarkStep(pos.pos, self.mark)
+
+    def to_json(self):
+        return {
+            "stepType": "addNodeMark",
+            "pos": self.pos,
+            "mark": self.mark.to_json(),
+        }
+
+    @staticmethod
+    def from_json(schema, json_data):
+        if isinstance(json_data, str):
+            import json
+
+            json_data = json.loads(json_data)
+        if not isinstance(json_data["pos"], int):
+            raise ValueError("Invalid input for AddNodeMarkStep.from_json")
+        return AddNodeMarkStep(
+            json_data["pos"], schema.mark_from_json(json_data["mark"])
+        )
+
+
+Step.json_id("addNodeMark", AddNodeMarkStep)
+
+
+class RemoveNodeMarkStep(Step):
+    def __init__(self, pos, mark):
+        super().__init__()
+        self.pos = pos
+        self.mark = mark
+
+    def apply(self, doc):
+        node = doc.node_at(self.pos)
+        if not node:
+            return StepResult.fail("No node at mark step's position")
+        updated = node.type.create(
+            node.attrs, None, self.mark.remove_from_set(node.marks)
+        )
+        return StepResult.from_replace(
+            doc,
+            self.pos,
+            self.pos + 1,
+            Slice(Fragment.from_(updated), 0, 0 if node.is_leaf else 1),
+        )
+
+    def invert(self, doc):
+        node = doc.node_at(self.pos)
+        if not node or not self.mark.is_in_set(node.marks):
+            return self
+        return AddNodeMarkStep(self.pos, self.mark)
+
+    def map(self, mapping):
+        pos = mapping.map_result(self.pos, 1)
+        return None if pos.deleted_after else RemoveNodeMarkStep(pos.pos, self.mark)
+
+    def to_json(self):
+        return {
+            "stepType": "removeNodeMark",
+            "pos": self.pos,
+            "mark": self.mark.to_json(),
+        }
+
+    @staticmethod
+    def from_json(schema, json_data):
+        if isinstance(json_data, str):
+            import json
+
+            json_data = json.loads(json_data)
+        if not isinstance(json_data["pos"], int):
+            raise ValueError("Invalid input for RemoveNodeMarkStep.from_json")
+        return RemoveNodeMarkStep(
+            json_data["pos"], schema.mark_from_json(json_data["mark"])
+        )
+
+
+Step.json_id("removeNodeMark", RemoveNodeMarkStep)
diff --git a/prosemirror/transform/replace.py b/prosemirror/transform/replace.py
index 7507531..0a41ffd 100644
--- a/prosemirror/transform/replace.py
+++ b/prosemirror/transform/replace.py
@@ -116,8 +116,22 @@ def fit(self) -> Optional[Step]:
         return None
 
     def find_fittable(self) -> Optional[_Fittable]:
+        start_depth = self.unplaced.open_start
+        cur = self.unplaced.content
+        open_end = self.unplaced.open_end
+        for d in range(start_depth):
+            node = cur.first_child
+            if cur.child_count > 1:
+                open_end = 0
+            if node.type.spec.get("isolating") and open_end <= d:
+                start_depth = d
+                break
+            cur = node.content
+
         for pass_ in [1, 2]:
-            for slice_depth in range(self.unplaced.open_start, -1, -1):
+            for slice_depth in range(
+                start_depth if pass_ == 1 else self.unplaced.open_start, -1, -1
+            ):
                 if slice_depth:
                     parent = content_at(
                         self.unplaced.content, slice_depth - 1
diff --git a/prosemirror/transform/transform.py b/prosemirror/transform/transform.py
index a52e045..1f50351 100644
--- a/prosemirror/transform/transform.py
+++ b/prosemirror/transform/transform.py
@@ -1,11 +1,11 @@
 from typing import Union
 
-from prosemirror.model import Fragment, MarkType, Node, NodeType, Slice
+from prosemirror.model import Fragment, Mark, MarkType, Node, NodeType, Slice
 
 from . import replace, structure
 from .attr_step import AttrStep
 from .map import Mapping
-from .mark_step import AddMarkStep, RemoveMarkStep
+from .mark_step import AddMarkStep, AddNodeMarkStep, RemoveMarkStep, RemoveNodeMarkStep
 from .replace import close_fragment, covered_depths, fits_trivially, replace_step
 from .replace_step import ReplaceAroundStep, ReplaceStep
 from .structure import can_change_type, insert_point
@@ -460,6 +460,19 @@ def set_node_markup(self, pos, type, attrs, marks=None):
     def set_node_attribute(self, pos, attr, value):
         return self.step(AttrStep(pos, attr, value))
 
+    def add_node_mark(self, pos, mark):
+        return self.step(AddNodeMarkStep(pos, mark))
+
+    def remove_node_mark(self, pos, mark):
+        if not isinstance(mark, Mark):
+            node = self.doc.node_at(pos)
+            if not node:
+                raise ValueError("No node at position " + pos)
+            mark = mark.is_in_set(node.marks)
+            if not mark:
+                return self
+        return self.step(RemoveNodeMarkStep(pos, mark))
+
     def split(self, pos, depth=None, types_after=None):
         if depth is None:
             depth = 1
diff --git a/pyproject.toml b/pyproject.toml
index 598976e..9466db0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ pydash = "^5.1.2"
 pandoc = "^2.3"
 pytest-cov = "^4.0.0"
 isort = "^5.11.4"
-codecov = "^2.1.12"
+codecov = "^2.1.13"
 coverage = "^7.0.5"
 ruff = "^0.0.230"
 
diff --git a/tests/prosemirror_transform/tests/test_trans.py b/tests/prosemirror_transform/tests/test_trans.py
index 462f28e..962c24a 100644
--- a/tests/prosemirror_transform/tests/test_trans.py
+++ b/tests/prosemirror_transform/tests/test_trans.py
@@ -949,6 +949,45 @@ def test_will_insert_filler_nodes_before_a_node_when_necessary(self):
         assert tr.doc.eq(doc(h(), b(p("One"))))
 
 
+def test_keeps_isolating_nodes_together():
+    s = Schema(
+        {
+            "nodes": {
+                **schema.spec["nodes"],
+                "iso": {
+                    "group": "block",
+                    "content": "block+",
+                    "isolating": True,
+                },
+            },
+        }
+    )
+    doc = s.node("doc", None, [s.node("paragraph", None, [s.text("one")])])
+    iso = Fragment.from_(
+        s.node("iso", None, [s.node("paragraph", None, [s.text("two")])])
+    )
+    assert (
+        Transform(doc)
+        .replace(2, 3, Slice(iso, 2, 0))
+        .doc.eq(
+            s.node(
+                "doc",
+                None,
+                [
+                    s.node("paragraph", None, [s.text("o")]),
+                    s.node("iso", None, [s.node("paragraph", None, [s.text("two")])]),
+                    s.node("paragraph", None, [s.text("e")]),
+                ],
+            )
+        )
+    )
+    assert (
+        Transform(doc)
+        .replace(2, 3, Slice(iso, 2, 2))
+        .doc.eq(s.node("doc", None, [s.node("paragraph", None, [s.text("otwoe")])]))
+    )
+
+
 @pytest.mark.parametrize(
     "doc,source,expect",
     [
@@ -1051,3 +1090,37 @@ def test_delete_range(doc, expect, test_transform):
         doc.tag.get("a"), doc.tag.get("b") or doc.tag.get("a")
     )
     test_transform(tr, expect)
+
+
+@pytest.mark.parametrize(
+    "doc,mark,expect",
+    [
+        # adds a mark
+        (doc(p("<a>", img())), schema.mark("em"), doc(p("<a>", em(img())))),
+        # doesn't duplicate a mark
+        (doc(p("<a>", em(img()))), schema.mark("em"), doc(p("<a>", em(img())))),
+        # replaces a mark
+        (
+            doc(p("<a>", a(img()))),
+            schema.mark("link", {"href": "x"}),
+            doc(p("<a>", a({"href": "x"}, img()))),
+        ),
+    ],
+)
+def test_add_node_mark(doc, mark, expect, test_transform):
+    test_transform(Transform(doc).add_node_mark(doc.tag["a"], mark), expect)
+
+
+@pytest.mark.parametrize(
+    "doc,mark,expect",
+    [
+        # removes a mark
+        (doc(p("<a>", em(img()))), schema.mark("em"), doc(p("<a>", img()))),
+        # doesn't do anything when there is no mark
+        (doc(p("<a>", img())), schema.mark("em"), doc(p("<a>", img()))),
+        # can remove a mark from multiple marks
+        (doc(p("<a>", em(a(img())))), schema.mark("em"), doc(p("<a>", a(img())))),
+    ],
+)
+def test_remove_node_mark(doc, mark, expect, test_transform):
+    test_transform(Transform(doc).remove_node_mark(doc.tag["a"], mark), expect)