FreeCAD is a free, open-source parametric modeler. I have been using it for my yoyo company since 2021, including 15 yoyo models that I’ve had manufactured or prototyped.
It has its own collection of tutorials: Tutorials - FreeCAD Documentation
This short video series talks about design/physics/manufacturing of yoyos. A must-watch.
Here’s a playlist that walks through the entire process of taking a yoyo design from concept to production. The resulting yoyo was the Mk1 Spyglass.
This thread has a lot of useful information as well, many other folks have designed/produced their own yoyos and shared their stories on these forums.