TMUX pane tabs, or 'locking/freezing' pane splits in place - tmux

Question

When using tmux, I generally have an editor open in a split on top, and a shell at the bottom. Right now, I'm writing a python script, and on the bottom half of the split I can't find a way to toggle back and forth between ipython and bash: the best I can do is create a nested split between those two, sharing the bottom half of the screen. Right now this looks something like the following.
Is there something like tabs within a pane, so I can switch back and forth between bash/ipython while keeping the editor locked/frozen in place at the top? It's not ideal right now to have to choose between switching to a new tab for one of the shell prompts or using these tiny splits. Tmux is so flexible it seems like there'd be a way to do this straightforward pane-lock. Thanks

Answer 1

Resolved using nested tmux sessions. I based my solution on a much-stripped down version of nested-tmux. I launch a nested session and then use tabs within that nested session. To launch a nested session, I use the following script tmux-nested.sh (adapted from the nested-tmux repo):
#!/bin/sh
TMUX_PARENT=$(basename "$TMUX")
TMUX_PARENT="${TMUX_PARENT%%,*}"
export TMUX_PARENT
_SOCK="r$RANDOM"
tmux -L "$_SOCK" new-session -s "$_SOCK"
This creates a nested session with socket given a random filename (a hardcoded value wouldn't permit multiple nested sessions, say in different tabs in the parent session).
In my .tmux.conf file, I add the following line on startup to change the tmux prefix for nested sessions:
# nested session logic
if-shell '! [ -z "$TMUX_PARENT" ]' 'set-option -g prefix C-b'
(where my normal prefix is a backtick)
EDIT:
I expanded this function into a much more robust implementation, which can be found below:
# Nest tmux sessions
tmux_nested() {
local usagestring='usage: tmux-nested [-n | -a nested-session-# | -l]'
if [[ -z $TMUX ]]; then
# ensure invoked within active session
echo "'tmux_nested' should be invoked inside an active tmux session"
return 1
fi
# read flags and check for number of existing nested sessions
local nested session_name
nested=$(tmux list-sessions -F '#{session_name}' | \
ggrep -P '^nested[\d]+' --color=never | sort -V)
while getopts ':lna:' opt; do
case $opt in
l)
[[ -z $nested ]] && nested="No nested sessions running"
echo "$nested" && return 0;;
n)
# if new session requested: create, set <C-b> tmux prefix, and attach
for (( i = 1;; i++ )); do
# get lowest available numeric value for new session name
if ! tmux has-session -t "nested$i" 2> /dev/null; then
session_name="nested$i" && break
fi
done
tmux new-session -ds "$session_name"
tmux send-keys -t "$session_name" \
"tmux set prefix C-b" ENTER "clear" ENTER
env TMUX='' tmux attach -t "$session_name"
return $?;;
a)
# attach to specified session if requested
session_name="nested${OPTARG}"
if ! env TMUX='' tmux attach -t "$session_name"; then
echo "Try 'tmux_nested -l'?" && return 1
fi;;
*) echo "$usagestring" && return 1;;
esac
done
# incorrect invocation, report incorrect invocation and exit
echo "$usagestring" && return 1
}