Yes, I have seen the several artist fields in my test file.
Then I performed the "merge field" action on two files and had a single artist field with all the entries separated by \\. I then executed the replace action on one of the files and got a single artist field with several names in it, separated by comma blank (no wonder).
For the other file I only pressed save and all the merged artists where separate ones again.
I take it that the op does not want to get multi-value fields and so wants to replace the double backslash with something else that mp3tag on save does not interpret as separator between fields.
(I think we had a similar discussion in
\\ problem
So: how do you merge multi-value fields so that they stay merged?