Hello jlanglais42, You’re correct you can only be in control of one device at a time. However all of your other devise will still run as long as their device mode is set to auto. Being “in control” of a device will just allow you to view/edit all of its programming, schedules, and other settings in the rest of the app. Currently you cannot combine the two timers to be controlled simultaneously. However if you create a manual program for each of them starting at the same time they will water at the same time. Please let us know if you have any other questions. Thank you!