This is an excellent tool, very handy.
Here are some things I have noted in-use:
1 - If the bones have certain characters in the name like '-', the group selection does not work
2 - The tool allows empty groups to be created - if you click and create without any bones selected
3 - Why use alt-Click to create? Why not just Click? I have tested the revised script logic and it seems to work OK. The 'Click' just checks if the Group button is empty or not and then decides to create or select
4 - If you free-up the Alt key, then you could use the following key combos/logic (or similar): alt-Click to redefine a single Group button (Assign new selected bones + Prompt for rename -or- Clear the button if no bones selected), ctrl-alt-Click to remove the button (
i.e. clear it and shuffle it along to end)
5. Also .. I agree with @hayasidist. Could potentially have a "Show Only" type check box - behaving somewhat similar to Lukas's "Toggle Color Bones" script
6. Also also .. I think the ' + ' buttons make more sense with 'Click' logic