In my opinion, non-core functions like these should be written by users (not Manifold), and shared on an open-source basis.
The most Manifold should do, I think, is check and validate, but even that is not necessary.
I suggest that you write a detailed spec for each of the functions you want. Inputs, outputs, corner cases, and above all, data (the curlier the better).
Someone might (a) write what you need or (b) show you how easy it is to write what you need.
The only hard thing is clear specification. That is actual real work, which is entirely up to you. ("Oh but it's well known. The name is enough." No it's not. Specify.)
Manifold engineering makes implementation easy.