Anyone know if custom domains are supported via the Workspace app configuration? Only the default domain (company.cloud.com) shows for me. When I try to add the custom URL it wants me to "log into citrix gateway and configure a responder action using the gui..." However, we dont have access to the Citrix Gateway in our daas.

Is it configured in the Access tab, under "Workspace URL" and/or "Custom Workspace URL" ?

Yes, it is

Yes, its supported. I believe it is a gateway service feature, and if your gateway is not enabled in the console that might be the issue.