I have a Ultrawide monitor (21:9 aspect ratio 3440x1440px) and my colleagues find it annoying that when I share my screen on Zoom, Slack, Google Meet etc. it will get zoomed out so the wide aspect ratio will fit on their regular 16:9 monitors. In addition to that I often find that I like to keep something like a meeting agenda on the same screen without necessarily having it visible to meeting participants.
Does anyone know of a piece of software for Mac OS that will allow me to assign a portion of my screen (i.e. the 16:9 bit, so the first 2560px in width and all 1440px in height) and let me expose that to screen sharing apps as an additional "virtual monitor". With Quicktime screen recording you can select a portion of the screen to record. I'm looking for something similar that will allow me to pipe that portion of the screen into screen sharing applications.