Typical case:

I add a new artist because one of this name already exists (and I think they are different), while doing so, I add some external links, let's say a Bandcamp link or a FB link.
If one of these links is already in the database I expect the editor to alert me.

Basically it should display all entities having the link (so it would also work for releases or release groups).

Something like:

 

ArtistB

https://thelinkthatalreadyexists [warning: already associated to ArtistA]