I think I solved your issue by mistake, namely inkscape not loading files made with graphics+.
I was looking for a way to make svg files for my laser software at work, long story, and stumbled upon your topic and tried graphics+ for myself. Everything was fine, as i don’t need to open the svg files with inkscape myself so I didn’t know about the not loading issue and my goal was to never touch inkscape and just do everything with rhino.
The problem was my laser software was also not liking the files made with graphics+, wrong fills and missing curves and such.
After some trial and error in the website JSFiddle - Code Playground I figured out that the problem was that the syle (stroke, fills and such) were contained inside lines starting and ending with “defs” and they were referenced by lines starting with .cls and an object ID if I’m not mistaken.
Excuse my ramblings, I don’t have much programming experience apart from grasshopper and some simple python stuff. Anyways, I managed to rewrite the files generated in graphics+ with grasshopper and solved the issue with my laser software, still needs some testing.
After I got it working for myself I was curious to try your example file and looks like I solved your issue aswell by mistake.
Here is the gh file, I explained almost everything I did in english, let me know if you don’t understand something. I originally wanted to write it in python but for now it still goes over my head, I’ll get there eventually.
For anyone looking at the file, please don’t laugh too hard at my noobiness, hey, it works, I think!
The gh file is very specific to the way the graphics+ plugin creates svg files, so it will more than likely break after an update.
Edit2: Updated file svg export fix.gh (35.6 KB)