You can now toggle lightbar brightness back and forth between 5% and 100% by pressing L1, L2, R1, and R2 at the same time. Settings are saved for each controller in text files:
ux0:data/vollightbarctrlwds4/p1config.txt
ux0:data/vollightbarctrlwds4/p2config.txt
ux0:data/vollightbarctrlwds4/p3config.txt
ux0:data/vollightbarctrlwds4/p4config.txt
The number within each file indicates the brightness percentage that that controller's lightbar will have. The files will be created automatically after replacing v1.2 skprx with v1.3 skprx and then restarting the system.
You can also manually adjust the number in each text file if you want something other than 5% and 100% brightness, but changes will not take effect until you restart the system. If you do set your own value that is not 5% nor 100%, pressing L1, L2, R1, and R2 at the same time will not change the brightness anymore. That functionality will come back after manually changing the value back to either 5% or 100% in the text file and then restarting the system.
Thank you aliihsanasl for this idea to allow for an extended ds4 batterly life.