This project is very cool, but I also think it was kinda possible on X11. However not as easy and that's why this project is exciting for me.
I tried to hack on tabbed from suckless [0] with a little utility to achieve a similar behavior. An X11 proxy that would rewrite window creation so that the parent window would be tabbed xid and not root window [1]. It kinda worked, but I never finished this for transient windows.
So you would start with a terminal inside tabbed instance with tabs hidden. The terminal would be behind chrwin proxy. Then when you launch anything inside, it would become a new tab and tabbed would switch immediately to it. There could be a possibility to kill the terminal after spawning a new client. But I intended to just leave it by default so you would go back to it.
Edit: that was my first approach. I wanted then to not rewrite window creation, but to reparent it afterwards. Something like this. It was supposed to simplify transient window handling, because the client would take care for it. At least that's what I remember.
I tried to hack on tabbed from suckless [0] with a little utility to achieve a similar behavior. An X11 proxy that would rewrite window creation so that the parent window would be tabbed xid and not root window [1]. It kinda worked, but I never finished this for transient windows.
So you would start with a terminal inside tabbed instance with tabs hidden. The terminal would be behind chrwin proxy. Then when you launch anything inside, it would become a new tab and tabbed would switch immediately to it. There could be a possibility to kill the terminal after spawning a new client. But I intended to just leave it by default so you would go back to it.
Edit: that was my first approach. I wanted then to not rewrite window creation, but to reparent it afterwards. Something like this. It was supposed to simplify transient window handling, because the client would take care for it. At least that's what I remember.
[0] https://tools.suckless.org/tabbed/
[1] https://github.com/hadrianw/chrwin