I’m pretty new to NixOS (a few months) but i could envision using Nix to declarativey configure tmux windows and panes in a dev shell. That said, Nix feels like it might still be too clunky at this point in time to quickly re-declare window and panel arrangements. But I never tried and it could be possible.
This actually works!
In other words, this probably won't directly involve changes to ghostty.