Infuse only supports two libraries, and they are "Movies" and "TV Shows." There's also "Other," but let's be frank--if your stuff ends up in "Other," you're probably dismayed with the amount of work ahead of you, and will likely do nothing about it.
On the Apple TV we can add these favourite libraries to the homescreen, but should we want to add another well-defined group of media that falls outside of these two limited definitions, we need to add a favourite folder. The main difference between these two types of favourites is performance. Favourite libraries are backed by an index and load very fast; favourite folders are backed by directly reading the source and load VERY slow.
Allow us to define any number of arbitrary libraries with whatever name we please, so that we can leverage the significant performance gains of having an indexed library. In addition, by allowing us to define a library, we should also be able to choose a source for retrieving all the metadata for these libraries, because as it currently behaves, Infuse just makes a best guess that an item belongs in the "TV Shows" library or the "Movies" library. If Infuse gets it wrong, though, there's no ability to move it (https://firecore.com/forum/topic/19750). To summarize, we should be allowed to define our own libraries, and more importantly, define the metadata sources that power the matches within those libraries.
In my case, favourite folders are effectively useless, as they don't load. I have too much content in them for Infuse to load them in any reasonable amount of time: I remember clicking on a favourite folder and waiting about twenty minutes before giving up and cancelling the attempt. Infuse needs to work on its ability to read folders, but this is another suggestion outside the scope of this one.