To test/run your AppStudio Projects in QtCreator, use the AppStudio Player environment.
We have included all of the AppStudio Tools under the Tools/External/AppStudio menu.
Make your main qml file the active document, then browse to Player (or hit alt+P) to launch the project.
You can use the other shortcuts to upload your app to ArcGIS Online, or make a build request without leaving QtCreator.
For more information, see here: What is Qt Creator?—AppStudio for ArcGIS Desktop Edition (Beta) | ArcGIS