I am not sure if you I have found a bug or not.
When I add a post function condition, I find I cannot add a grouped condition until I have added a second condition.
After the second condition is added the grouped condition icon becomes active. Unfortunately, when I then click the Grouped Condition icon, it takes me back to the Add Condition view. I must then add a condition and when back in the condition tab I need to delete the original condition.
Am I doing something wrong? Using Jira Core Server 7.6 and also Jira Core Server 7.8