Just a speculative guess, but does:

[\+]

work any better than:

\+

?

Just a speculative guess, but does:
[\+]
work any better

While you're at it, try plain

[+]

since the + sign has no special meaning in grouping brackets. Unless, of course, Windows 11 has invented its own flavor of RegEx. (Wouldn't put it past 'em. For comparison purposes, it was a hideous shock to learn that in BBEdit, the ampersand & has a special meaning in replace patterns. 8,000 guesses how I learned this.)

Edit: It's also worth trying the double-escape \\+

Sadly...

[+] returned everything
[\+] returned nothing
\\+ returned nothing

And for the sake of trying everything, \\\+ also returned nothing :-(

8,000 guesses how I learned this.)

Probably the same way that I learned DELETE * FROM table WHERE foo='bar' isn't the same as DELETE FROM table WHERE foo='bar'... :-O

Still can't find a solution, so how about an alternative...

I use Notepad++ for coding. And if you use Ctrl + Shift + F you can search for all files in a directory that contain FOO, and apply filters to restrict the search to specific filenames.

Under "Filters" I usually use:

*.php *.css *.js

to restrict it to PHP, CSS, and JS extensions.

Any thoughts on how to also say and the filename doesn't contain a +?

I've tried several variations like this with no luck, and I'm not sure that it's possible:

(*.php *.css *.js) && !\+
(*.php *.css *.js) && !*\+.*

Since I don't have to escape the . then it's obviously not a regex, anyway, just a series of wildcards that are pre-defined. But I can't find that predefined list anywhere.

I found a thread in their forum about it as a feature request, but that was in 2015 and I couldn't find anything more updated.

I also downloaded Total Commander in the hopes that it would be able to do a search and exclude the +, but no dice.

this would be trivial using unix commands.

instead of "regular expressions" or "wildcards", do some research on "file globbing" and perhaps you will find a sufficient windows solution.

EDIT:

Never mind ... realize this was about Win11!

This works in Win7 *+.*

Well, @phranque... that took me down the rabbit hole :-O

Best I can tell, the only way to accomplish this is using PowerShell:

Get-ChildItem -Recurse | Where {$_.Name -match '+'} | Select Fullname

[shellgeek.com...]

My end goal was to move them to some other directory, or maybe even delete them, so I'm not sure that this query is going to actually help me. And I'm never going to remember that ridiculously complex format in the future, anyway. But it answers the question, so maybe it'll help some future googler :-)