Ref T5474. The first rough cut of triggers showed some of the trigger rules in a tooltip when you hover over the "add/remove" trigger menu.
This isn't great since we don't have much room and it's a bit finnicky / hard to read.
Since we have a better way to show effects now in the drop preview, just use that instead. When you hover over the trigger menu, preview the trigger in the "drop effect" element, with a "Trigger: such-and-such" header.