Xfrog is procedural. open a .xfr (its a text file) and you will not see any polygons. You will see parametric values for Xfrog.exe to draw. and the file will be about 2 kb. e.g. 2 sheets of paper.
the conceptual problem with being able to add, for example a polygonal teapot, would mean that the .xfr would no longer be parametric, it would be a blend of parametric data and a list of triangles.
basically we tried to create Xfrog "pure" parametric text files.
if you want to, for example, hang a complex structure as a leaf on every branch, you first model the desired form in 3.5 and then save that using "save item = subhierarchy" . and then import that into your existing 3.5 model where you want to use it, e.g. as a "leaf" in this case, using File: "insert item" and you can really make anything with Xfrog, if you try long enough
. the author, bernd lintermann, has made sunglasses, a housefly, many buildings, etc. i guess we should consider to release his "non-plant" xfrog models
i hope this helped a little ?