Almost anywhere that you would use a latch or compliant latching mechanism you could use magnets.

I print nameplates for my office worker friends and add a few under the surface to give a place to put loose paperclips. Also, in bag clips (for chips and stuff) so they can stick to the fridge when not in use.

It’s like bearings and assorted bolts, you just keep a stock of them handy because they’re so useful in general when you’re making things.