Right now I use a trill for notating a shake. It’s not the same thing. Generally you see a shake as a squiggly horizonal line above the note that you want it on. It is used mainly in brass parts.
If I understand correctly what you are looking for, you would like to have a squiggly horizontal line that looks like a trill line without the tr. marking. Have you tried to create a playing technique with continuation line that triggers the proper playback technique (if needed)? My guess is that would do exactly what you are looking for, and you could even save it as default (star button) to keep it for future projects. Please tell me if you need more details.
Not sure if this is the glyph you want…
or this one: