PPS: one more trick. Once you’ve established how many possible combinations there are for each number, you can easily compile these in a spreadsheet. Here’s a start, using “one” (there would probably be many more combinations):
Note that you are always thinking in terms of the user. Choose key combinations that require minimal consultation of the documentation, and create ligatures that follow this.
You can then generate ligature names using the CONCATENATE function, and copy-paste this list into your OpenType generator function in FontCreator. You’ll still have to do some copy-paste, but this batch function really shaves off the time.
Florian’s fonts are much more elegant in their creation, since he uses more contextual alternates and composite glyphs. My method is more brute-force, but it doesn’t require quite as high of a font IQ! 