Through this project I realized that there's just some limitations to a plain tmux config. I eventually had to switch over to calling out to shell in order to get around those issues.

Commit with the switch to shell here: https://github.com/saysjonathan/dwm.tmux/commit/c8752b978390...

I think there's a lot of potential to scripting terminal multiplexers in various ways and I would love to see more work exploring what's possible!