There's not a good way to exclude direct bookings with an Everything But type trigger. For that to work you'd create a custom listing source and set that on all of your widgets and inquiries and bookings (if you have it on a widget, it'll flow through to inquiry and booking automatically, but if you created a manual booking you'd need to set it manually).
Instead of that, I'd recommend rephrasing it as an only trigger and pick all the listing sites you want, then uncheck Airbnb.
We've got plans for a channel source overhaul that will split out channel and listing site, and then let you target direct bookings separately in criteria, but no ETA on that yet.
