It is very beneficial to be able to store all custom FME work between versions and installations. FME has "FME Shared Folders".
However, while this works for connections, transformers et.al., it apparently doesn't include custom formats developed with e.g. Python.
My suggestion is to add this possibility to the "FME Shared Folder" functionality.
Basically it would just require FME to scan a few additional folders during startup, so it's not that big change, I think.
Cheers.