Select an object (or several) to bring up the editbar at the bottom — resize in mm, lift, rotate, turn into a hole, or delete. Ctrl+Z / Ctrl+Y undo & redo.
A plain-English set of commands (nicknamed "shuf") that builds a model step by step by driving the same controls as the mouse. Every object gets a number the first time it's created — use select N (or select N1 N2 N3, or select all) to choose exactly what later commands act on; creating something new always replaces that selection. Indentation is purely cosmetic; write comments with # or // anywhere on a line. "Save .shuf" downloads everything done this session, by hand or by script.