One of the things that bugged me for a long time is that every now and then for some shapes, when editing their text, the draw.io web interface puts in trailing line feeds after the text, messing up layout.
The easiest way to work around it is by searching inside the diagram XML for
"".
(the above code got screwed by WordPress.com saving it, so the search is in this small gist below)
This behaviour is intermittent on the drawio MacOS desktop app.
–jeroen