How to add apps to the system tray (not the shelf)

Call me crazy, but i was sure on a previous chromebook that i was able to add apps to my system tray (the menu that comes up when clicking on the clock). I cant find anything about this online, and all discussions center around adding apps to the shelf. I know how to do that. but how can (or can i) add apps the system tray?...i believe in the past, i was able to add the scan feature to that tray. on my previous chromebook, i had 2 pages worth of apps in that area.

any help would be appreciated

Scott
chromebox 4