Welcome @Programmierer!
I totally agree with you, and I’m pretty certain this will be added to the game. @tom mentioned in one of the livestreams that they would probably implement something like this to make it easier to know how big the structure is that you’re drawing.
So, yer 
I am pretty confident we will see this (hopefully sooner rather than later 
)
Edit: Double ninja. @froggy @Steveadamo you win this one.