I'm biased but I like Trizbort for Windows. It's specific to parser games, though I suppose it could be used as a flowchart for Twine games. Also, Twine may be its own mapping tool if you just concentrate on creating nodes.
Jason Lautzenheiser has been adding features and fixing bugs, and it's on version 1.582 now. Trizbort lets you use a lot of keyboard shortcuts to build a world. I was able to use it for pretty much all the ParserComp games.
I also think Trizbort is really good for planning out an area and updating what you have. You can color rooms/regions and, with the next revision, add subtitles.
This is a link to a released binary. I wouldn't be surprised if a new version comes by in 2 weeks.
For Mac users, apparently Trizbort can run under wine. I have no clue how a Mac user would get it running, but it can be done.