What are the libraries for adding elements to the graph by the user?

Question

JavaScript

For example, there is such a graph. The user clicks a button and an unattached element appears. The user transfers it to the connection of elements, say, A and B, and the element stands between them, that is, "A - element - B". Or the user can simply attach it to another element by creating a new link, say A - B - element. I found many libraries, but nowhere was it possible to embed a new element between two old ones.

Answer 1

I found many libraries, but nowhere was it possible to embed a new element between two old ones.

Because that's not possible. First you need to break the ties, and then form new ones, otherwise nothing will work. The library cannot know what you want from it, so you are provided with the functionality for displaying, and you yourself modify your graph as you need.