Sorry you are having a problem with this. Can you please confirm if the below workaround works for you?
You should be able to specify a port in the Migration Scripts repository URL field. For instance, to specify port 8081 I would add the following:
If you have already connected to a Migration Script location but against the wrong port, you will need to unlink and re-link your database from source control to be able to edit the Migration Script URL.
Sorry this is convoluted, we will look into making this easier in the future.