Step 1: Decide what you want it to do. Open the Shortcuts App and create a new shortcut that opens an app, sends a message, performs an action or two, gets directions, or opens your wallet. Shortcuts can do so many things, and it's worth exploring the app and creating a really useful one.
Step 2: Make Back Tap run the shortcut. Open Settings > Accessibility > Touch > Back Tap > and choose the shortcut you created. You can set different shortcuts for double or triple taps. That's like having 2 secret buttons!
Sometimes I activate it accidentally, but it's not that bad and it doesn't happen all the time. I have a double-tap set to open my camera and triple-tap to create a new note. Hope you get some use out of it!