How do I make a simple automation to run a device for 10 minutes in the new app?

SmartApps & Automations
6

Just use a simulated switch and have that switch coming on be one of the conditions for your piston. Then turning the switch on will run the piston.

If you put the simulated switch in a smartthings scene, you can also make it a widget.

See the community FAQ:

FAQ: How to Run Scenes and Automations (2018 V3 App)