I built a tiny Windows desktop app to hide files on my lap top from anyone who might be using the lap top briefly - visiting in-laws, friends who wanted to check email, etc. Building it was triggered by a nosy but technically un-savy sister who was always poking around.

This was about 8 years ago and I use it on all my machines since, even work ones. It 'hides' files by randomly renaming a folder's contents and removing the file extension. Simple, but surprisingly effective.

I called it Cloak My Stuff.

https://badwolfsoftware.com/cloakmystuff.html