I know Keyboard Maestro. I know there are workarounds to everything. But many complex applications that I use daily allow users to customize their shortcuts (Steinberg Cubase, Avid Media Composer), independently of the macOS which is (1) broken as you can see from the example above and (2) subject to change at any moment on the whim of someone at Apple.
If you read the example above, with screenshots, you can clearly see that the feature is exposed as a menu entry and yet is broken. I refer you specifically to the exchange above between the developer and the head of support: it’s handled by the OS, so we can’t do anything about it.
I started this thread because I couldn’t (and still can’t) find any sense in the keyboard shortcuts chosen for the DT3 beta (and the abandonment of the toggle behavior for source/preview). But I don’t think there’s any point in a general debate about who should implement keyboard shortcuts, not in this forum anyway. I’m going to let the DT polish the beta and not worry about new features request.