I managed to sometimes have commands been send to tmux by using the following:
VtrSendCommand! "echo hi" You need to call this without exec or call in your .vimrc.
The problem is that it still sometimes thinks there is no pane to attach to. Also it does not work with variables. For example I currently run test this way: exec g:bjo_test_runner g:bjo_test_file (Some projects use Minitest and some Rspec so I need this flexibility ) But when I parse those into VtrSendCommand it sends the following to the pane: g:bjo_test_runner g:bjo_test_file So it does not actually replace the variables. Still not sure if thats something im doing wrong, or a bug in Tmux Runner.