Is it possible to validate maxlength for page titles?
And if not are there other possibilities?
You can upvote a feature request here: https://kirby.nolt.io/281
Nothing really straightforward, I’m afraid, apart from the options mentioned in that feature request.
Not sure if it can also be achieved via the custom add fields plugin:
Also it does not have the same function but as workaround you can try slugs.maxlength option