I wanted a part once, but didn't know how to make it for FZ because there are no comprehensive instructions for new parts. It actually took so long to work out how to convert to FZ - PDF to svg to FZ - that it would have been quicker if I leant Inkscape and just drew it from scratch.
If you are an Inkscape expert you can make parts very quick, then you just have to make them conform to FZ XML requirements.