Fork length (axle to crown) is measured along the direct line from the fork crown to the center of the front hub. This dimension can be displayed in BikeCAD Pro, but it is not how fork length is meant to be input. When fork length is input into BikeCAD, the fork length dimension is meant to be measured according to this diagram.

In the Dimensions dialog box, fork length dimensions are shown minus sag. The concept of sag is explained here. If you are using a rigid fork, there will be no sag. Therefore, Fork length - Sag = Fork length.