Currently, global search does search for text within notes, but it doesn't give any indication where the search string was found within the note, which makes it useless for large notes. An alternative would be a separate search field for notes.
I've had response from Enpass back in 2018 that this feature was already on the roadmap, but it never materialised. I don't think this is very unusual use case, there are few other queries in forums requesting the same feature. Currently, to search within notes I have to edit the note, copy all text, paste to notepad, then search in there - hardly an elegant solution...