Very nice feature to have. Thank you! I've found, though, a couple small issues when you rename an existing Action group.
When you rename an Action Group, it appears at the end of the list the next time you open the dialog box unless you remember to 'Save'. I don't think the order should have to be saved.
Renaming an Action Group will subsequently exclude it from any saved configs. Looking in the .mtg files I can see that the old name is left there.
After renaming a group, it no longer appears in the drop-down list of executable action groups.