This suggestion seems good, there’s just some minor issues to solve.
Script currently looks like this:
#!/bin/bash
pgrep Ardour >/dev/null
if [[ $? -eq 0 ]]
then
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/presentation-mode -T
else
notify-send "ardour is not running!"
fi