Until recently, wasn't the Action Groups panel modifiable from the Options dialogue?
One thing that you can no longer do is change the checkmarks in the Action Groups panel without actually applying the changes to one or more files. That's a problem.
Say you apply an Action group that doesn't get used very often (for instance: "Remove All Fields") to the files you're working on. Now you want to clear that checkbox so that next time you don't accidentally apply it. You can't do that any more.
Or you have a standard set of actions that you normally use. You go in and clear them all, select some other non-standard Actions and apply them. Now you want to reset the checkboxes to the standard set. But you can't do that any more.
An alternative that would address this checkbox problem would be to save the checkboxe states, even if "Cancel" is pressed in the Action Groups panel. I'm not sure that would be desirable for everyone, though.