To make nice sophisticated vector libraries, you should use Inkscape (or similar applications) and spend time learning how to do it.
However, you can make your own vector libraries by hand crafting .svg code like a rugged pioneer/explorer.
Here is a starter kit:
one-shape.svg, two-shapes.svg and two-shapes-grouped.svg were made by Layer → Import/Export → Save Vector Layer as SVG with just that particular symbol of the library on the vector layer.
Then, the .svg code for the vector shape content (not the administration stuff all around it) was copied and hand cobbled into the My-Little-Vector-Library.svg symbol list section.
Compare the individual ‘shape’ .svg file contents with the corresponding symbol library section in My-Little-Vector-Library.svg. You’ll see and understand what the relevant content is.
A multi-tabbing syntax highlighting editor is the ideal tool for this task.
(Syntax highligting is for city folk, rugged pioneers don’t need it.)
@DannyDA I suggest that you try it. It’s ‘not difficult’ and the worst you can do is waste your time trying it.
@Takiro Plug-ins are for city folk