Does there exist a good tutorial on creating custom IFX libraries and uploading them to Windchill?
They're not exactly tutorials, but in the Help Center there is information on customizing libraries for IFX, as well as steps on how to upload libraries to Windchill.
I hope that helps!
there is also a video available.
If you search for 'IFX Windchill' you also will find some useful posts.