Question: I’ve noticed that some inactive projects still appear in the mobile app (Android, iPad or Win10 app) and are ‘greyed’ out. How can I delete those or stop them appearing? 

Answer:

That occurs when you were subscribed to the project and now either:

• You are no longer a member of the project, or
• The project is not active.

Past/inactive projects are shown that way to indicate the app is storing data that is unnecessary if you'll no longer be using it. When you see that, you can unsubscribe from the project to delete the data from your device.

The method for unsubscribing from a project is described here.