You can replace the .STL files in the directory: Bambu Studio\resources\model
You must match their naming conventions with this workaround. So for example, remove the original STL’s and store them for safe keeping. Insert new model files with the same exact names.
It’ll be confusing. There are probably some configs to see if we can populate the menu with new items but I doubt it’ll be something I hunt hard for.
My workflow doesn’t need a right click create generic primitive, so unfortunately not a priority.