You can't do it yourself on the app, but there have been reports that the blue umbrellas can issue a Return Time for your next park.
I have not tried at WDW (cancelled my recent trip and rarely hop anyway), but I have done this a bunch of times at Disneyland. As recent as the last month or so. It is very nice to have the ride for the other park lined up before I hop over to the other park. I usually shop a bit on the way out of the park so it is nearly ready by the time I make it to the other park.