Make a button open an app

A button can open an app such as Spotify, Netflix, Uber, the Camera or Maps.

Select the button in Edit mode.
Set When tapped to Open an app.
Type the app's name in Find an app (for example Spotify) and tap it in the list. The phone's own apps like Camera, Messages, Mail and Maps are at the top.
On the Android app you can switch to Apps on this phone to pick from what's installed.
Tap Use and try the button.

Good to know

The app has to be installed on the phone you're using.
App not listed? Type its link (like spotify:) into the box. On iPhone you can also use a flow with Run an iPhone Shortcut and a Shortcut that uses Open App, which opens any app.
Picking an icon like Camera sets the matching action for you.