I noticed something very unusual today.
If you switch an app in Editor mode to the Staging resource, this also switches the live published/public app to use the Staging resource!! I tested this a couple of times using data I knew to be on Production but not Staging and it appears to be the case.
This somewhat defeats the point of having a Staging resource for development. If I switch to Staging while developing, my users are also then editing data in the live copy of the app on Staging, not Production?!
In the meantime, we will have to develop changes against Staging in entirely separate copies of Apps and then shift changes by way of app link not release workflow…