As JHainer mentioned, layouts do become handy places to lay things, related to our layout work, as well as to temporarily hold other things, like groceries (maybe I'm alone on that regard.)
Here are the two spots on the layout that often get loaded-up with parcels, etc. They are both along the entrance aisle between the cellar-to-garage door and the cellar stairs to the first floor. In the first shot, at the suburban neighborhood area, all those locomotives are normally parked there, showing off, but get moved out of the way if I am not running the layout for a spell. Also, if you look carefully at the foreground of the second shot, of the long narrow section of Moon Township, you can see some crafting miscellany that's been set into the middle of the roadway for the moment. That flat roadway there at the neighboring track are tempting spots to lay things temporarily.
Regarding rolling stock and engines being all over the place, from time to time, since I run ten separate loops and often change the trains out, to protect them when I am working or resting things on the layout, I drive them all into the tunnels, on parallel tracks and one behind the other, so they are out of harm's way, and park them in the tunnels until the coast is clear.
FrankM, Moon Township, USA.