You can add your own reservations manually in the latest Google Trips update which has just started to head out to users as Google recently pushed the update to the Play Store. If you use Google Trips, you'll now be able to insert reservations for Flights and Hotels just in case you have a reservation that wasn't tied to your Google account, or if you weren't the one who made the reservation but you're still part of it. The app update pushes Trips forward to version 1.0 and also adds in some other new features to look forward to.
Now when you open the application you should see the Floating Action Button at the bottom of the screen and after tapping this you'll see the options to add the new flight, the new hotel, or just a simple note if you already have a reservation or something else that's being stored in here and you want some extra information to add to it. For those that plan on using this app or continuing to use it, the FAB button is not located on the home screen, rather you have to set up a trip, then tap on the "reservations" tile that is located in that trip, and there is where you'll find the FAB button to manually add your reservations. In addition to the manual capabilities Trips also now automatically parses bus and train reservations from Gmail just as it does for flights and hotels. This way if you tend to take trains or public transit for your transportation needs Trips can still keep you covered.
Other than those larger changes mentioned above the only other things included in the 1.0 update seems to be bug fixes and improvements as noted by the Google team responsible for the upkeep of this application. There isn't any detail about what sort of improvements these were, nor about what bugs were fixed, but what this breaks down to is that the app should run smoother now, and that's always something to celebrate. The app update is already live on the Play Store so if you already have Google Trips installed, simply go into your my apps section and tap the update button, or if you need to install it, you can grab it from the button down below.