Use as other user/permissiong-group

I want to test a permission group on the SG website using the “Use as” menu item.
It prompts me to enter a “User/Permission Group”, but if I try to add my test user (not active) it doesn’t appear in the dropdown, and NO permission groups are available to test with.

Am I not able to test page designs without using another active user and adjusting the permission group to suite?

I’ve noticed this too, Permission Group is not an option.
You need an active user to test on.