The original module was enough for newlib, which strictly followed this model in the file system hierarchy. The lesstif HID also hardwired this two-level tree structure in the GUI.

In pcb-rnd this has been replaced with a new struct type called library_t that can represent an arbitrary tree: directories and files within directories down to many levels.

Both the gtk and the lesstif had has been modified accordingly and can properly display the tree. This in turn enables alternative footprint backend implementations such as fp_wget to import more complex libraries, e.g. the one on edakrill or gedasymbols.org.