Editor "magic" URL flags?

Hi again, @richard or anyone who knows,

In class lately, I’ve been using the ---multi URL flag to open the micro:bit editor for programming a radio transmitter on the left side and a receiver on the right side, using the simulator for lack of enough hardware;
https://makecode.microbit.org/—multi#
(The same would be interesting for 2-player Arcade games, hence the this post in this Arcade category…)

I am not able to figure this out, but is it possible to make a link which opens one shared project in the left editor window and another shared project in the right window?

Also, I am still curious whether it would be possible to make a link that opens a shared project directly to the textbased JavaScript editor, ref. my previous post?