All I need at home is a couple of sidings, as I don't really do serious operation. The layout fills the bookcase so the sidings need to overhang (over the printer and hamster cage!). A slimline, low-profile design was needed.

This is the result - a discrete tapering shelf, which attaches to the layout using the same split hinges. OK, the shelves need tidying, but the layout is reasonably neat. But if that is still too intrusive, simply lift the end up...

By use of some paste-table type hinges (left over from a previous incarnation of my son's trainset) the fiddle yard swings up, and over...

Until it is stowed over the layout. When I've made a lighting pelmet for the front of the layout the stowed fiddle yard will be largely hidden.
I had planned to make this a simple deck for a point and a couple of tracks, however this would have meant very short trains if the board was not to hit the ceiling! (Yes, I did check). The front edge track entry position, and tapering front edge, also made a useful arrangement of tracks tricky. However I realised a sector plate would work well - albeit, is more complex to make, especially as it has to hang upside down!

The deck of the fiddle yard is a double thickness of PVC foamboard, the top layer forming the sector plate supported on the lower deck. As seen here a lip was fitted to the rotating edge of the plate in a slot in the deck, supporting it when upside down - and hopefully ensuring no vertical movement of the deck tracks relative to the entry track.
Talking of track, the next job is to lay some!