When configuring Workspace / Identity Manager you can decide to tick the box “Hide Domain Drop-Down Menu”
This is great as for your end users as they no longer have to pick a domain. You can even go one stage further and untick “Show the system domain on the logon page”
This results in a nice clean logon for users as below with the benefit they no longer have to select their domain.
However as I was recently playing with this and made the changes, I had a blind panic moment in which I realized I didn’t know how to get back in to the system-domain to make any more changes
To get back to the system domain you can use the url https://fqdn//SAAS/login/0
To be clear this is in the documentation, it just took me way longer to find it than it should.