Habmin is very important for administering zwave devices as it provides features and capabilities unavailable in PaperUI. But all other parts of Habmin have received minimal to no updates for the past couple of years. For example, the Rules builder there still creates OH 1.8 style Rules. I would not be surprised if that editor has also no received any updates and has finally stopped working.
There are examples of doing something similar using HABPanel. Design your SVG floorplan or dashboard for HABPanel with Inkscape