Addon to encrypt history and bookmarks
I remember another ticket about this but cannot find it. Anyway, this addon seems to be the solution: https://addons.mozilla.org/en-US/firefox/addon/link-password/
It can encrypt both TBB history and bookmarks which is great especially considering both are without any kind of protection implemented.
To upload designs, you'll need to enable LFS and have admin enable hashed storage. More information