Assembly3 workbench is yet another attempt to bring assembly capability to FreeCAD. There is the original unfinished Assembly workbench in FreeCAD source tree, and Assembly2, which is an inspiration ...

Don't use this repo if you care about py2-support and support of freecad < 0.18. If so please have a look at the traditional workbench structure. This is a template for a FreeCAD workbench / module.