It would be useful for migration and removal the old repositories with option to get them back again in the easy way.
The same feature is present e.g. on VM hypervisors. One can remove the VM from the console but leave it's image on the disk for further use.
Another option could be looking like this:
When you add a repository from directory, SCM lists all new found repositories. And then you can select those ones that should be added to the UI.