It is part of the classical notation, and are used for an 'interesting' move. Today we can get the engine evaluations, but back in time strong players annotated games with these signs: ! ? !? ?!
!? was typically used to highlight an idea you did not have time to analyze properly, a move that may be great, but you are not sure, a psychologically great move, or ...
Dubious but difficult is a nice way to think of it.
From what I've seen, "!?" is most commonly used for a last-ditch effort play in a hopeless position (especially where the refutation is not immediately obvious), or moves that are just plain odd and hard to evaluate. It is also sometimes used for moves that are quite risky, but more often than not these fall into one of the two aforementioned categories.
This mean your brain like rabbit brain.
what does the !? move mean and whats its name its on the emoji in game analysis setting