Tree Sheets is a two-dimensional note taking software, a nested spreadsheet. It reminds me of mini cubes.
I tried it out, it is nice. It uses an opaque format, so it seems, but whatever.
It's like a spreadsheet, immediately familiar, but much more suitable for complex data because it's hierarchical.
It's like a mind mapper, but more organized and compact.
It's like an outliner, but in more than one dimension.
It's like a text editor, but with structure.