Manually trigger the display mode popup (I don't know what it's actually called)

This. How do I trigger this from the command line? I’d like to trigger it with a launcher on a panel.

Hang on, I’m a professional luser.

I looked in the launcher for display settings, found that the command was xfce4-display-settings, then did xfce4-display-settings --help

it helpfully informs me that the flag is -m for minimal.

Right click panel > Panel > Panel preferences and drag n drop “Launcher”. Now Right click the launcher > Properties > General and add the “Display” application. Click on the pencil icon and edit command to xfce4-display-settings -m.