This is an endless loop. I see your screen shot to add a co-host; however, there's no other instructions on how to land on the page that give you an option to add a co-host. I go to my listing dashboard, as you show on your screen shot; however, I dont' see co-host option. Host Assist is a bit confusing, I would think co-host option would be a natural add to that page or the profile page, or security page. But no, none of those pages contain adding a co-host.
I would be ok to change my login from Facebook to email/password. That way I can give my husband the login info and he too can manage the host page. However, I dont' see how I can do that!