Custom SF Symbols

Is it possible to use OmniGraffle to create a custom SF Symbol, as described here?

From the description: Step 2: Edit the SVG file in a vector-drawing app.

When using OmniGraffle as the vector-drawing app, the exported template has stripped or otherwise mangled the template version number. Consequently, the SF Symbols app can not read the template.

I will try the Sketch app next, which is supposed to support SF Symbol templates, but I would rather use OmniGraffle if possible. Thanks.