Layer shapes: bring to front, send to back
Overlapping shapes stack in the order you drew them - the newest on top. Right-click any shape for Bring to front / Send to back to reorder that stack without redrawing anything.
Draw two overlapping boxes - the second one drawn sits on top, covering part of the first.
Right-click the first (bottom) box and choose Bring to front. It now renders on top of the second box - a real change to draw order, not just a visual toggle.
Send to back works the same way in reverse. Layering only changes which shape sits on top of which. Devices and links have their own layering, and shapes sit behind them by default.