The MM.ListTools code overall looks good to me. Thank you for the comments, documentation, and examples :)
For Sort with Index, even though computer science curricula devote like a month to teaching the different sorting algorithms (or at least they did back in my day), actually developers don't very often implement their own sorts. Better to use APIs that are already tested and optimized. As you probably saw, there's a VuoListSort_VuoGenericType1 function, but that wouldn't give you the indices for your output port. Instead, you could use std::sort like here.
My only other suggestion for MM.ListTools would be to call VuoGenericType1_curve in Morph Point List (as you did in Scale List to Center).