I think it was mentioned above but the way you have it setup, the .pdx already has both simulator code and playdate code. If you right click on the pdx file and select Show package content you will see both the dylib for macOS and bin for the Playdate hardware.
So what is missing for your mockup is the ability to launch on device after building. There are some solutions for this here but I agree, it should be added directly in the Nova extension together with the option to build in Release i.e. without Simulator binaries and without debug info.