This has always been the Hard Problem. For one, constructing an ontology that is comprehensive, flexible, and stable is huge effort. Then, taking the unstructured mess of documents and categorizing them is an entire industry in itself. Librarians have cataloging as a sub-specialty of library sciences devoted to this.
So yes, there's a huge pile of tools and software for working with knowledge graphs, but to date populating the graph is still the realm of human experts.
When you boil it down, the current LLMs could work effectively if a prompt engineer could figure out a converging loop of a librarian tasked with generating a hypertext web ring crossed with a wikipedia.
Perhaps one needs to manually create a starting point then ask the LLM to propse links to various documents or follow an existing one.
Sufficiently loopable transversal should create a KG
So yes, there's a huge pile of tools and software for working with knowledge graphs, but to date populating the graph is still the realm of human experts.