Save this as a script, but change all occurrences of xfce4-terminal with your regular terminal name:

#!/bin/bash



if [[ $(pgrep -x xfce4-terminal) ]]; then     xdotool windowactivate `xdotool search --pid $(pgrep -x xfce4-terminal) | tail -1`; else     xfce4-terminal; fi

And add a shortcut that executes that script. This might differ depending on your OS.

On Xubuntu you can enter the path to the script into Keyboard/Application Shortcuts.

You might need to install xdotool if you haven't already:

sudo apt install xdotool

In my tests this opened the terminal in which you executed the last command.