Thanks for the replies,but.....
This is rediculous - the terminal tip and the encrypted disk are such cumbersome answers to a basic problem ( assume for just a minute that I'm not a terminal jockey😀 ).
I want to click onto a small app or prefpane, be promted for my password, enter it, and then be able to make a file or folder invisible.
Then open the app again, passwords again, and have a list of files I've hidden and be able to make them visible again.
Simple.
Someone must have written a prog to do this - or have I stumbled onto a goldmine in the waiting - sadly I know not how to program🙁 🙁