I believe the encryption that we have in Logseq is to encrypt and decrypt the actual files - this is useful when you are storing the files in the Cloud and you do not want anyone to be able to read the .md files.
The ability to hide/lock the content (a block or an entire page) - at least from the UI. The actual file at the backend - well we can have a different discussion about this because it might corrupt the data if it’s not done precisely.
I have started a side project to build a plugin for Logseq. My direction was more of password-protected pages, but from what I can see and hear, at least the ability to hide the content would be really helpful for now. What I built has nothing to do with encryption, it’s just an overlay to hide the contents. If I have the time, I will add a feature where a password is required to unhide the page content.
Check it out; Plugin to lock pages and I hope if it helps anyone here.