Paste a picture straight into the text box (Ctrl+V), or add one here. It goes in as a line like [image 1 60% "Fig 1: Plant cell"]. Click a picture on the page to resize it, move it or make it a pencil sketch.
Flowchart between [flow] and [/flow]: one line per path, like (Start) -> [Add] -> <Is it even?> and <Is it even?> -yes-> (Stop). (…) start / stop, […] step, <…> question, /…/ input / output. Write [flow across] to draw it sideways.
Tree between [tree] and [/tree]: one node per line, children indented under their parent. Short labels get circles; add circle, box, plain or arrows to choose. A line like A -- D joins two nodes (for a graph).
Chart between [chart bar] (or line / pie) and [/chart]: one Label: value per line; Label: 4, 6 for two series with series="2024,2025". Add "Title", x="…", y="…", a width like 70% or mono for ink only.