Reviving this old question - there is now a feature to do this.
Snap! v7.0 was released in December 2021, and has "block reducing" as described here.
A project creator can (1) create custom block palettes, or (2) filter/hide the blocks that are shown in the block palette. One of the options is to hide all blocks that are unused in the current ...
For a book, I like The Linux Command Line. There is a YouTube series, The Missing Semester. You can pick and choose the lectures that you like.
There are an abundance of cheatsheets online.
Most importantly, you need to have the experience yourself. You've got to have the knowledge, and master it well enough to adapt it for your audience.