A release is made once every few months and appears on our official Downloads page as a stable build. Everything else is unstable, made by the community for testing. The keyword after “RawTherapee-” is the name of the feature branch, e.g. dev, newlocallab, etc.
New features in the dev branch will be present in the next release. New features in other feature branches may or may not be present in the next release.
We try to maintain backwards compatibility between stable releases when possible. There is absolutely no intention of maintaining PP3 compatibility between development builds.
Read:
Whatever new things there are in the latest development builds from of dev branch will most likely be present in the next release; this includes the new Shadows/Highlights tool. PP3 files from the latest dev might not be compatible with 5.5, i.e. they might lead to different results.
To find out which features might make it into the next release, refer to Issues · Beep6581/RawTherapee · GitHub