Hey Kyle,
thank you for your quick post. I'll give it a try, but I got it working with the following settings:
Disabled AutoActions
Enabled Group-Change in CB-Sub-Plan
Enabled Field-Change in CB-Sub-Plan with CB-Field-Plugin
Enabled AutoGroup-Change upon field specified for plugin
now, the group-assignment works for a user who is in Group "Registered" and another Sub-Group "GroupA". The user is assigned to group "GroupA-Sub1" when paying the subscription and falls back to groups "Registered, GroupA" when sub ends. This didn't work first, because I had all users only in group "GroupA" but not in "Registered". Using both Groups gets it working fine.
Maybe this is helpful for others, too...
I think, it would be goog to redesign Auto Actions for CB 2.0 as it is a great timesaving tool, but it seems to have some problems.
Thank you for your help anyway!!
Best regards, Stefan