A desk needs to be able to be BOTH a shared AND a secondary seat. They are currently both usage types, for which you can only make one selection.

The situation is such: employee X uses shared desk #1 on Mondays and shared desk #2 on Tuesdays. We need to assign Desk# 2 as a secondary desk for this employee, but cannot because you can only selected EITHER "shared" or "secondary". They should not be mutually exclusive.