How do I replace \\ (double backslash)?

This is the syntax that the forum software (Discourse) and its comment parser is using.
This has nothing to do with the Mp3tag software itself. Therefore, no information can be found in the Mp3tag documentation.

BTW: If you use the search function in the upper right corner in this forum and use search words like "replace double backslash" you would find some existing entries like Find & Replace double backslash?