This functionality is only available as part of the MobilityPlus eXperience with an EVdX subscription. (read here how to find your subscription type in the app)
Tap on the tile of your car on the app's home screen
In the screen that opens, go to the settings via the cogwheel at the top right
At the bottom of the screen that opens, tap on Disconnect car.
A confirmation question will be asked, which you confirm by tapping Disconnect.
If desired, you can indicate to delete the data collected by Enode. To do this, check the box. The mileage readings are always retained in the app.
Your car will again have the status Ready to connect
If you want to connect another car with the app, click here for the procedure.