Use case - I need to mark to which client issue belongs. Every issue is required to have one and only one customer assigned.
I tried do it with custom fields - but in team-managed project you are limited only to 55 options.
This field change to frequently to do it as global custom field.
So I tried Epics. One Epic = One client.
In team - managed project I have created configuration where parent field is required for all issue types other than Epic.

But this doesn't work. On create or edit screen parent field is not marked as required and the Jira allows to create issues without parent link.
There is no validator in rules, automations fails to..
Have anyone ever had similar problem and found a solution for that?