It's a fun format that's easy to generate, but after trying to do complicated things with it.. you kind of understand why. It's underused b/c
- Complex graphics render different in different browsers. So you can't rely on it shows up the same (never had the same issue with a PDF for example)
- There are quite a few renderers but they typically don't implement large parts of SVG b/c it's too complex.. So you can never really be sure what parts are "safe" to use.
- Large complex graphics display extremely slowly (again, compared to a PDF)
- There is basically one editor.. Inkscape. And it's got it's own quirks and doesn't match Chrome/Firefox's behavior. Ex: You can add arrows to lines in Inkscape and they don't display in Firefox
It's also just got too many weird corner case limitations. For instance you can embed a SVG in another SVG (say to make a composite diagram). But you can't embed a SVG in to an SVG in to an SVG. On the web if you inline or link an SVG you also end up with different behaviors
> There is basically one editor.. Inkscape.
Do you mean in terms of open source vector editors? As there a wide variety of tools with SVG authoring/editing capability, among the most well-known being Adobe Illustrator, Sketch, Affinity Photo/Designer, even some web apps are available that were made for online SVG editing (eg: SVGator).
Inkscape, like some tools such as Affinity's, adds its own XML namespace with custom attributes and values, though for arrows I would expect it to use native `marker` elements.
It's certainly true that with SVG's flexibility and particularly with cross-browser handling differences/bugs it can become its own task to get consistent presentation when doing more complex things with it. Still very fond of the format.
Inkscape is the only major vector graphics editor that relies on SVG as its native file format. Most other apps are merely allowing you to import/export SVG files which is often a lossy process (e.g. vector objects with filter effects might get rasterized).
SVGator is focused primarily on animation and it's rather pricey. Boxy SVG might be a better choice if you are looking for a web-based SVG editor (disclaimer: I'm the developer).