When you are location in the window where you are setting permissions for a specific category by member group, if you delete one of the lines of permissions that you added before, then it takes you all the way to the Category Permissions screen under the admin Gallery Configuration settings after you click the delete button.
When you delete a line of permissions it should just delete those permissions, but the navigation should not change, and you should remain in that same category permissions window in case you want to make other changes to the permissions for that category.
The way it is now, you have to spend time after you delete permissions to navigate back to the category permissions window where you were, which is wasted time and mouse clicks to get back there.