> 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).