I started adding the beginnings of bar plots (the red squares above) to show the number of techniques/question available for each topic. The problem with this is that it's very hard to get a quick overview of what's missing: a user has to drill down into each section and remember what's there (sensible display of some of this in with bar plots might help, but it's still not great). But thinking about it, what would be good to show is an actual tree: for a given starting point (such as a topic: speciation rate), and then all possible descendants (such as all possible questions for this topic). Those descendants available in methods/software get one branch color (say, black), those not get another branch color (gray) [though it might be good to distinguish those present in methods but not software]. Here's a hand-drawn example for the basic idea:
And with colors and labels:
Under this approach, it's easy to distinguish areas with methods/software available (black/solid) from those lacking methods or software (gray/translucent). In the example above, the central dot represents a topic, the first circle represents questions, the second circle criteria, the third perhaps character type, etc. Derrick Zwickl had the good suggestion to allow users to set the order in which options are plotted; I'd also like to allow users to fix certain values (only look for missing methods under a likelihood criterion, for example).
Well, we'll see how it goes. As with all posts, please feel free to make suggestions in the comments.