Ask HN: Tool recommendations for graphs instead of tree mindmaps

I like mindmap software for how intuitive it is, but if I want to enter and manipulate data that's a graph rather than a tree I haven't found a tool I like. Any recommendations? If it can handle flow left to right where physical layout has a meaning I would like it even more. Something I can work with low tech people on, where it can scale to hundreds of nodes but I can select only some to display at a time. Thank you.