I left my computer on last night and when I came back this morning, my trays were gone. I was using Tray 1. Now I can only get Default to appear although Tray 1 is still in the Window dropdown. Can someone tell me what I did?
Perhaps if you click or maybe double click the Tray 1 icon bottom left of your screen it may come back.
This is the option, “Be careful of the planet! Don’t leave your computer on for nothing all night!” Next time, I’ll delete everything! 
Thanks.