Use password protection to limit access to shared notes.
@appotry welcome to the forum.
This is a comment made by Laurent (the project owner) during beta testing in reply to a similar question.
Note sharing worked. Any selected note, when shared, can be viewed as a web page. I appreciate this is very new and being developed but notes are currently shared without access control.
I don't expect this to ever be any different. I feel supporting a password wouldn't make sense because the password is the share key (the URL ID). I guess if someone requires extra security they can always send a part of the URL via one channel and the second part via another one. Share keys are a 32 characters nano-id, and it would apparently take "more than 1 quadrillion years needed, in order to have a 1% probability of at least one collision", so that sounds secure enough.
Here's the relevant section of the FAQ:
tl;dr is, there isn't that option yet, and for good technical reasons there probably won't be in the near future.
If you're interested in the reasoning behind that, there's plenty of discussion about that in the forum.