A Harmonyscene can have as many guides as needed, but you can only use one guide at a time. You can decide which guide you're using by selecting it from the guides list. The selected guide will display in your drawing space.
Although you can select the active guide at any time, a guide will only behave as active if one of the following drawing tools is selected:
Once a guide is active, it will display its horizon line and vanishing points in your drawing space. There will also be two or three dotted lines following your mouse cursor in the drawing area: One line for each horizontal or vertical axis in your guide, and one line going from each vanishing point in your guide through your mouse cursor.