I created an iMessage app extension with the predefined Xcode template. I now want to add a 'normal' app to that extension. How should I proceed? I just tried to add a storyboard and a new scheme but it fails with following error:
The request was denied by service delegate (SBMainWorkspace) for reason: NotFound ("Application "mybundleid" is unknown to FrontBoard").
Add a new target of type Single View Application to your project:
Then select all source files (.swift, .storyboard) you want to use within your new app and tick the new target in "Target Membership":
Update:
After further discussion in the comments, I understand you want to:
This is not possible. The App shown in the project is actually installed but is hidden/not visible to the user.
The only way to install App and extension at the same time is to install an actual app.