Have you tried using tools like this or this or this?

Interesting, thanks, I did try a couple of other online SVG tools, but not the ones you suggest. From a very quick look, though, they seem to suffer from the same as the ones I tried: it is not obvious how (or cumbersome) to adjust the height, width, viewBox of the SVG so the path can be copied directly into the 1:1 ratio used by SH3D. And some of them do not to arcs very well either. So, my money is still on Inkscape for GUI path editing.

Getting arcs to work is what broke my head

And you are not alone. Arcs can be a pain, especially when the model size (ratio) is different from the viewBox 1:1. But arcs are also so beautiful, so I cannot help trying manually the few times I need them. There is a reason I keep the W3C: elliptical arc curve commands in my bookmarks. [:)] Now, as I am already in way over my head in elaborating the technical stuff, I should add that even if Inkscape will change arcs to curves when you edit the path nodes, it will only adjust the arc values if you scale/rotate the entire path. So a clever guess, some trying and failing + resorting to Inkscape in an emergency, usually will do the trick.

What I think is very nice, is reading suggestions such as yours in the forum. It is always interesting to see wishes from other users. So, please, not get me wrong, I do not disagree with you. An SVG editor would be useful/nice. But maybe not a frequently used feature? Which is why I have no opinion as to whether it should be a developer priority as really have no clue how much work it would involve. But there is some open-source code for SVG editing out there. For all I know, maybe it is possible the Batik path compilation tool used already.

ok