The Opening Drawing-mode, allows creation of Windows, Doors & permanent openings. Click the relevant opening type button on the left toolbar, or use the keyboard shortcuts, 'W" for windows, "D" for doors and "P" for permanent openings.
You can toggle between creating windows, doors & permanent openings by using the change typebutton in the guide-box or the Tilde change submode keyboard shortcut.
Opening type can always be changed at a later stage in the data-grid.
All openings are created on their parent walls, so to create an opening, left click on one of the openings edges, and left click again to finish creation. Right click to reset the original clicked point, and right click again or use the Escape key to exit the drawing mode. You can manually enter the width of the opening after the first click, by typing the width in millimetres and hitting the enter key.
Openings are named numerically in order of creation, so a handy tip is to create windows according to the window schedule naming so that you do not need to rename windows or doors at a later stage.