I'm curious how this relates to Skia (the library that handles cross-platform rendering for Chrome and Flutter). Seems like this could be an alternative backend but also could serve as faster replacement?
forma is geared towards vector-graphics heavy use cases. A very good example would be Lottie or Rive animations or games that make use of vector graphics. Another possible use case would be places where you need a very small software renderer, like an OS's early boot.
about a decade ago I wanted to get started prototyping gameplay with vector graphics and I was dismayed at the state of available libraries to do this efficiently. I'm glad things seem to be getting much better in this space!
How about 3D modeling programs, like FreeCAD? That's currently single threaded and doesn't use hardware acceleration so it could use the boost for sure.