In this way you can create additional dimensions (e.g. window sash heights and widths).
Step 1: Select in the toolbar Dimension -> Linear.
Schritt 2: Click on the starting point of the distance you want to measure. The cursor contains a yellow square when it "snaps" into the corner point.
Schritt 3: Click on the end point of the distance you want to measure.
Schritt 4: Use the mouse to move the dimension to the desired position.
Schritt 5: Click again to set the dimension.