This looks very interesting! It's great to see innovation in the terminal multiplexer space. tmux has held the crown for too long, and it's worth revisiting this space with modern approaches.
I really like the concept of quickly hiding and showing a pane, and spawning it for a single command that can be easily repeated with Enter. Quick scrollback editing is great as well. I often do this manually in tmux with copy/paste, or re-running the command with `tee`, which is a bit cumbersome.
One nitpick would be to have an option to minimize or remove the borders around panes. It's nice to have extra metadata around a pane, such as the CWD, but space is precious in terminals, and showing borders around every pane feels wasteful. Maybe this is already possible, I haven't looked at the docs yet. Will definitely give this a try soon.
EDIT: Ah, kudos for the nice roadmap[1]! It seems this might already be planned as part of [2].