Filter for Backslash in Artist Field?

How do I do this? I don't see anything in the Help file.

I tried putting it in quotes but it doesn't work.

Edit: Found this in another post and it works: "$meta_sep(ARTIST,'\')" HAS "\"

Then a short detour to the FAQs might have helped:

I checked yesterday and didn't see that.

It wasn't clear to me at the time that I needed to select "All" in the drop-down menu at the top to find it.