Gotcha: note assigned to widget or something

I spent quite a bit of time trying to figure out why a particular note on one of my controllers was not working on one rackspace. Seemed bizarre. Then while driving, it suddenly occurred to me that the note must be assigned to a widget or something.
When I get back to my computer I will look for that (I guess a widget assignment somehow/somewhere by mistake?)

And hence the “Show MIDI assignments” dialog, available from the Windows menu, designed explicitly to show you what assignments already exist.

But yes, the usual reason for a note not working is because it’s assigned to a widget (or a global control, if it’s not working in all rackspaces)