If you would need to set up your displays once every week or less using the GUI is just fine. I had to do it every morning and after a while it became really annoying.

Turn off the HDMI display:
[codesyntax lang="bash"]

xrandr --output HDMI1 --off

[/codesyntax]

Turn on the HDMI display and set it as primary display:
[codesyntax lang="bash"]

xrandr --output HDMI1 --mode 1920x1080 --primary --left-of eDP1

[/codesyntax]