Hi Hopki!
Good idea with the background, solved it in a first step this way.
Reason ist just an esthetical one. I have a textbox giving the caption of a node if there is one

When the text is very short, there is much space left in the grey background area which does not look good.
Using a transparent background has the problem of readability in some nodes.
PS:
'Solved' it: interestingly the height of the text-container IS somehow flexible with the option 'word wrap'. That's all I need so far.