Thanks for your message, Lon. There are two types of text in a PreFigure diagram. The glyphs you are seeing in the PreFigure output come from MathJax, which processes everything inside an #m tag. It may be possible that we can use a different font by passing a configuration parameter into our MathJax script. I'll investigate with our current use of MathJax and also as we (slowly) convert to MathJax 4.
It is also possible to include plain text not processed by MathJax inside a PreFigure label, and it seems natural that you would want this kind of label to be rendered in the same font as the surrounding text (I thought that's what you meant originally). This may rely on converting the output SVG, in which the text is included with a #text element, into TikZ. I've been experimenting with the Python package Rob linked to but haven't had success yet, but I plan to keep trying. Having PreFigure output TikZ raises a host of other questions.
I'll report more later.
Thanks again,
David