Hi @grum , welcome to Zynthian!
I think the easiest way to do that is via webconf, search the wiki if you don’t know how to access it. On the main screen, AKA the dashboard, under Hardware, click on the Display you have selected, then set Advanced View at upper right on, then add your statement to Config.
If that doesn’t do what you want, another option is:
May the Force be with you.