We all love a gadget at Christmas so how about these ?
Called Magna Couplings, they are rare-earth magnets on laser-cut swivels. Plenty strong enough to connect coaches, even 16mm scale ones, yet the connection can be broken by pulling the vehicles away from each other by hand.
I think this is really clever. Obviously if the plan is to shunt stock then it's less so but then how many people shunt on a garden railway?
I suspect this could be adapted for 4mm scale carriage use. The smallest of these magnets are about 2mm in diameter so the grab would be strong enough but not too strong. Under working corridor connections though, they would be a lot easier to deal with then hooks and loops.