I’ve never used a Mac (Windows & Linux PCs only), but I believe that unlike Windows it is not possible to have a system audio level setting for individual apps, unless you are using a third-party app to do this.
Is it only Shotcut where you can’t hear the sound? Or is it all applications?
If all applications see here:
If just Shotcut, then the only way I know of turning off the sound is by using one of the 2 controls I showed in the image above, or by applying the audio Gain-Volume filter on the clip, track or Master-Output. But if that were the case the Audio Peak Meter display would be empty.