Thanks for the quick response!
Exactly yes - the screenshots are from Obsidian.md, which renders mathjax. Typically a single ‘$’ renders inline, and a double ‘$$’ renders block/display.
This shows how inline and block render:
And this shows how the user inputs the expressions:
This chrome extension used to work really nicely, but broke a few years ago: GitHub - wonglkd/mathflowy: Chrom{e,ium} extension to provide MathJax rendering for Workflowy