When you get many splits going in tmux sometimes its time for a new layout.
There are four layout strategies that I use, main-vertical, main-horizontal,
even-vertical, even-horizontal. Almost always I am useing the main ones with
mod plus a or mod plus shift a keybindings.
bash
# Select Layouts
#―――――――――――――――――
bind -n M-a select-layout main-vertical
bind -n M-A select-layout main-horizontal
bind -n M-E select-layout even-vertical
bind -n M-V select-layout even-horizontal
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https://www.youtube.com/playlist?list=PLTRNG6WIHETB4reAxbWza3CZeP9KL6Bkr
Also check out this long form post for more about how I use tmux.