Hope you don’t mind my tuppence worth…
There is a way to combine the trays as pages on one visible tray with tabs at the bottom, this I believe is the most sensible way of exploiting this new feature.
First create the individual custom trays of your choice, then drag and drop them one at a time on to the first to be in the order you prefer then station the combined to the side
clicking the auto hide pin will activate the pages to hide on side, but clicking again to pin as visible will show the tab pages on the bottom as shown.
