Cannot delete group because in use by a firewall rule

I had this annoying issue as well. I managed to fix it by going through all my rules and turning on "Match known users". This allows you to see if you have previously assigned a user to a rule. If you untick "Match known users" after assigning a user, the rule will simply remove this user from it's logic but it's still attached to the rule, hence the inability to delete the user. Once you have "Match known users" turn on, you can remove the affected user by assigning the Any user to replace the user you want to delete.  

Managing multiple rules and filters is a nigthmare when you need to delete an object. On UTM9 was easy to find where the object was used and the option to enforce the removal was great.

They have to integrate it soon.

This is really quite cumbersome to perform this every time a user needs to be removed.  Has anyone discovered a better way to work around this issue or is there a case # that can be referenced?

This is really quite cumbersome to perform this every time a user needs to be removed.  Has anyone discovered a better way to work around this issue or is there a case # that can be referenced?