A wishlist for TeXmacs articles

It would be useful to have some short articles or tutorials covering the topics listed here below. This article collects them in the hope that someone will contribute them to the blog. They can also be considered interesting exercises to improve one own TeXmacs knowledge: learning by teaching. In case you manage to cover, even partially, one of the topic, please add a remark here to point to relevant material. If the topic is covered, move it to the “Already covered” section.