To remove
unnecessary trays right click on the tray list window and select Remove->… from the context menu appeared.
You have
the option to remove Selected, Empty or
All trays. If trays being
removed hold tiles inside, then those tiles are flushed to the background.
See also: Adding trays, Showing/Hiding
trays, Emptying trays, Renaming trays, Merging
trays.