On most of my layout, the tracks are easily accessible, so I use the RIX magnetic tool for uncoupling.
However, for the staging yards, I use the Kadee in-track magnets, and mark their location with a yellow post (styrene rod)…
A black stripe (decal) around the post indicates the location of the magnet, while two or more stripes indicate that there are magnets at the same point in the tracks beyond the one with the post.
The one shown below is on-layout, but is a bit of a reach from the operating aisle, so also indicated by a yellow post…
The delayed magnetic couplers allow the loco to spot the two boxcars at different doors of the factory, albeit not in the same move.
There are similar installations at hard-to-reach locations around the layout.
Wayne