Remove \\ from artist field

This one has been trying my mind today.

I have a few albums where the artist is listed in the following format mainartist\featuringartist1\featuringartist2 ... ect

Is there a way I can remove the \ and just add "feat." or "," to separate the artist names. I think the slashes look sloppy.

Could you check the tag of 1 field in the dialogue "Extended Tags" (Alt-T)?
I suspect that you see a multi-value field where the contents of the fields of the same type is separated by \\.
In the dialogue "Extended tags" such a multi-value field should appear as several entries for e.g. ARTIST.
To deal with such fields, you have to merge them with an action of the type "Merge duplicate fields". Specify a separator unequal to \\.
Then you can treat the field as a single field.