Thanks for the feedback. An excel course should be doable. Currently the most general way to write material is to use this: https://trane-project.github.io/generated_courses/knowledge_...
Basically a folder of lessons where the flashcards are pairs of markdown files.
There's also another tool to write simple flashcards and lessons in a json file, run a command, and build all those directories and markdown files for you, but I have not written the documentation yet. Here's an example for a course based on a reworking of Euclid's Elements: https://github.com/trane-project/trane-math/blob/master/cour...
But plain markdown files for now should get you going.