Collision Group Editor is currently in a state where it’s almost not usable. It has all kinds of different issues and glitches that are hard for me to describe. I listed a few of them below.
Once you create a new group, it doesn’t display itself (unless you force it to update the list):
Text boxes are not in focus, which introduces issues like deleting any selected objects if you press the Backspace key:
If you delete a group, groups around it don’t update their positions by themselves:
Scrolling is messed up. It either doesn’t let me scroll at all, or scrolls in a way that splits the Group Names and the 
s apart and/or glitches out:
If I try to rename it, the Group Name disappears, and doesn’t let me type. If I force-update it, I’m able to type, but once I press enter to apply it, it again disappears:
I’ve tried reinstalling Studio, to no effect.
I don’t know when it started happening.
It isn’t place specific, you should be able to edit any place and have similar issues.
Please note that these issues don’t always happen. Although rarely, sometimes it all works just fine, the group names update by themselves, you can rename them without issues etc.
But most of the time it’s just decides to work very poorly, giving a feeling as if the whole Editor would be made in just an hour or less, with not much thought put into its creation.