As of FlutterFlow version 5.0.9+, in Settings and Integrations > App Settings > Web Deployment > Custom Domain, there is only one Custom Domain per project.
The problem in my case is that I have already set up four different environments (i.e. Development, Test, Demo, Production) for my project, but I only have one Custom Domain (I was hoping to at least have two -- one for Demo and another for Production).
The other problem I have is when I make changes in an environment, say Development, and I have the Custom Domain URL set for the Demo environment, when I deploy Development, the custom domain URL will end up re-pointing from Demo to Development (which is not what I want).
Is there an upcoming fix for this?