It sounds like you want to switch to the OBS Studio App so you can switch scenes, etc. 

You may need to rethink your workflow a bit. Although you can't modify macOS to do what you need you can remotely control OBS. OBS has a websocket API and can be remotely controlled via a web browser but it can also be remotely controlled via iOS/iPad Apps as well as actual hardware controller boxes (stream deck or MIDI controller) with a myriad of programable buttons and dials to control OBS and a lot more.  You can add an inexpensive second monitor, even an old iPad setup as a second monitor and put OBS on the iPad. There's a great deal of potential solutions.