The best thing I have done for making my notes usable is to have a simple grep script that runs anywhere and searches all the notes files I have. My script is case insensitive and matches lines that contains all the strings you searched on.
Indeed. For Emacs users, there's consult-notes-search-in-all-notes which does that with file previews.
To that end I recently wrote about several modern ways to convert handwritten notes to searchable notes. I primarily write handwritten notes because of the mental benefits of doing so.