At least 2 problems were detected while testing MDL-49185.

1) Edition of existing (and used) registration leads to the Registration URL being lost on save.
2) Edition and Re-registration (multiple times) sometimes leads to the creation of multiple providers pointing to the same proxy.

Apart from that, in general... that "double" UI, with all those tabs... is pretty confusing IMO, but that's out from the scope of this issue. Just stating it's not clear at all.

Ciao