Alright, I’ve found out how to get the first instance of the outliner to include a properties region. I just copied some action editor code like do_version_action_editor_properties_region() and pasted it to versioning280.c, and modified it a little.
Now, I’m just not sure of which subversion number to use to contain the code so I just put it outside all MAIN_VERSION_ATLEAST(bmain, 280, ???)
Can someone tell me how to know which subversion to use ?
Well, it could overlap the restriction buttons instead of merely pushing them aside, and presumably my design would not require constant usage, as well.
To be honest with you, I don’t get why Blender uses a non-overlapping paradigm and that floating regions aren’t just used. Whatever issues could be thought of there is, undoubtedly, a resolve for it. I guess I have to just look into it more…