For OO structure, https://structure101.com https://structure101.com is fantastic at global views, especially for refactoring, where it can help you plan how to

For OO structure, https://structure101.com https://structure101.com is fantastic at global views, especially for refactoring, where it can help you plan how to transition from hairball to e.g., directed graph. It has a 30-day trial to show you it's worth the price. Rolling your own visualization is useful and not too hard. It drives you to frame your questions more narrowly (call-hierarchy/sequence diagram, data flow, sub-systems?). The fast-path for me is to generate the relation doublets/triplets (x --R--> y) and then let yFiles/yEd (https://www.yworks.com https://www.yworks.com) lay it out hierarchically after converting to their tgf "trivial graph format". yEd GUI is free; the yFiles layout library is worth 10X the price if you're displaying lots of graphs.