The plugin provides a shell script to either create a popup window if a session doesn't exist or switch to the session if it does exist. Requires tmux version 3.2 or greater and tpm.
In your .tmux.conf, add the following to install the plugin
set -g @plugin 'dtpike/tmux-scratchpad'
Then install all plugins (prefix + I).
The plugin doesn't automatically set a key binding to use the scratchpad.
Choose an unused key binding and set it to run the toggle command. This is
installed with the plugin in the scripts directory.
For example, add the following to bind prefix + p to toggle the scratchpad:
bind-key p run $TMUX_PLUGIN_MANAGER_PATH/tmux-scratchpad/scripts/toggle
Reload your tmux environment after setting up the key binding.