I struggled to remove a unused screen.
While trying to delete one, I always got the following error message
Cannot delete screen as it is used in Screen Scheme

I removed it from Issue Type Screen Scheme -> removed from Screen Scheme.
It did not fix the issue, I could not delete the said screen.
It appeared to not be used anywhere

What should I do to be able to delete once for all?
Spoiler answer : Check workflow where you might have used it, it might not been displayed but still in use in one of them as a transition screen.