This is the free version of the well-known MathMagic Pro . While the Pro version integrates directly into the InDesign menu, the Lite Edition is a standalone editor that lets you build equations and save them as images to place in InDesign.
Offered by Everway , Equatio provides a free tier for creating equations. While it is more geared toward accessibility, it’s a powerful tool for generating formula images. indesign math plugin free
While often subscription-based, check the Adobe Exchange for occasional "Math Pro" updates or community-developed scripts that offer SVG rendering from LaTeX code. This is the free version of the well-known MathMagic Pro