@Rene Voegeli, yes, we totally agree.
It makes sense to keep the UI simple. Maybe later on an advanced mode could enable some more complex features.
@Rene Voegeli, It reminds me the reference line function in CAD. It can be easily done technically. More of UI work, as we don't want to make the app looks like CAD software. We will come up a solution, and keep you updated.
When hanging curtains I'd like to be able to select the top of the window as a straight reference line and then offset the line by a specified distance (e.g. 5cm) above the window.
This way all curtains will be the same height from the window.