Hi,
recently I came into this topic because of some packages3D library contribution…
How to create a nice and geometrical correct 3D model for KiCad using OpenSCAD?
Then I discovered it is possible to export a real mechanical part as STEP model using OpenSCAD and FreeCAD together…
Luckily it is possible to convert a ‘.scad’ script to STEP using FreeCAD 
(not all the OpenSCAD functions are fully supported… Minkowski and Hull are some of them)
For importing OpenSCAD code/models one can follow this FreeCAD howto
https://www.freecadweb.org/wiki/Import_OpenSCAD_code
When the OpenSCAD model is imported in FreeCAD, the model will be a real mechanical model and not a tessellate approximation as STL format would produce…
From inside FreeCAD it is possible to manipulate the model and use StepUp to export both STEP and WRL for your 3D model to be used in KiCad …
I created this topic because I noticed OpenSCAD has many affectionate users… then I thought it was a pitty to lose user’s contribution to 3D library just because the 3D source model was not coming from FreeCAD or CadQuery scripts
Here a sample of what can be generated:
and the result
Hoping this could help contributors to the packages3D new repo
Maurice