exported PNGs are unsharp and lack arrowheads

[FDMS]

(An SVG export option would be even more useful …)

[bgrawi]

What browser/OS are you using? Right now the site is only tested in Chrome/Windows.

[FDMS]

OS X Safari. (In Windows Chromium (Torch), the exported PNG doesn't lack arrowheads but is very small, and in Edge or IE (not only) PNG export doesn't work at all in case you needed a tester.)