Can I plan repetitive dives on DecoPlanner Mobile?

Yes, repetitive dives are now supported through the "Logbook" section, which you will find in the main menu.
To plan a repetitive dive, tap the large + sign to plan your first dive. Then return to the Logbook page, where you will see an entry for the current day with the first dive listed under this day. To plan a second ("repetitive") dive, tap the smaller + sign on the day entry. This will open up a new planning page, where you will now find a "Surface Time" tab to the left of the active "Levels" tab. Enter your surface interval here, and then plan your repetitive dive as usual in the "Levels" tab.