Google Inbox has a Trips feature that bundles reservations. You can add an arbitrary email to an existing one of these Trip bundles. Inbox automatically creates new bundles when it detects reservation emails.
My wife and I are planning a new trip, but we're in the early stages, so we haven't actually reserved anything yet, so there's no bundle for our trip. Inbox won't let me add an email to Trips without picking a bundle. How can we manually create a new Trip bundle?