Step 5 : create the king post (in a new body)

In this new body, create a reference plane from the XY plane.
Its position in Z (normal to the starting plane in the local reference frame) is

    <<SketchOpening>>.constraints.WallHeight
              + <<SketchRoof>>.Constraints.UnderTrussBeam

In a new sketch created in this plane, create geometries necessary
for the octagonal profile of the king post.

Create an extrusion with a length equal to

        <<SketchOpening>>.constraints.WallHeight
               / 2 * tan(<<SketchRoof>>.Constraints.RoofAngle)
                    - <<SketchRoof>>.Constraints.UnderTrussBeam + 150mm

In a new sketch created in the YZ plane and from the master sketch
"SketchRoof", create the geometry to carve the tip of the king post.

Create a pocket across everything by symmetry.

Still in the YZ plane, and in a new sketch, create the geometries
needed for the mortises.

Create a pocket by symmetry of the thickness of the tenons to be embedded.

Create a circular copy of the various pockets around the Z axis.