I am using the Playground more and am working on VR stuff, so I use the Oculus Quest to do my development. It works fine when I publish and send it to my headset via Firefox sync, but it would be nice if I could type stuff on my pc and be immediately updated on the headset.
I imagine it working like Google Docs does when docs are shared, with multiple cursors.
adding @RaananW
Oh, that would be a very nice feature! Which we sadly don’t offer yet. We can add that to a future list of features, I think it will be a nice thing to have one day 
About XR debugging specifically -
When I am implementing XR i first do whatever I can on the desktop with the emulator. until I get to the point that the emulator cannot help me anymore. I then switch between my desktop, an MR device (Lenovo explorer on desktop) and my quest. The quest is mainly there for me to test with a great device that i trust (and has ALL of the XR features babylon supports). the MR device is used to replace the emulator and give me basic XR testing environment. The quest has the playground opened (I am using the oculus browser and not firefox) and i just reload a new playground when needed.
I couldn’t find any way to debug INSIDE XR when on the quest, so the MR device is very helpful here as well.