Unable to create more than one display

I have recently picked up a Meta Quest 3S to use as a remote desktop when working with astrophotography equipment. The first thing I have done is set it up to use the Mixed Reality Link remote desktop. All the articles I have read suggest that I should be able to open up to 3 virtual monitors but I cannot get it to add additional displays after the first one is connected. The "Add Display" button is disabled.

I have tried this on two different machines. My Dell XPS 17, and the fanless MeLE Quieter 3 which is what I actually want it to work with out in the field so to speak. What am I doing wrong? Why is the "Add Display" button disabled.