How to add custom errors to $error variable in laravel?

Question

Laravel

Hey!
There is validation via $validate, which, as you know, redirects back in case of an error, and puts the list of errors in the $errors object. So, in order not to produce various conditions in the form, I would like to add my own errors to the same $errors object, which may already be after the validator. For example, checking whether it is possible to use such and such a name or whether it is already in the database. I tried to return redirect()->withErrors - but here the errors are entered into the session, not into $errors. And I, as I already said, would not like to do one more check - are there any errors there, and also output them, if any. How is it done correctly?
Thank you!