8) Now in Border subobject, activate the Select and Move tool and select the hole. Hold Shift key and move it in Z axis, this is going to create new polygons.
9) After this, use Select and Uniform Scale tool to flatten those edges. Repeat the same process more 2 times.
10) If you find necessary, move the vertices of the corner between the layer and connector for a smooth result.
11) Now select this polygons in both sides:
12) Still inside the Polygon subobject, click one time in MSmooth tool and the polygons of your selection will be subdivided by a local Mesh Smooth. With this we are going to have a median-smooth transition from the layer to the conector.
13) If you wish, resize the polygons in the connector not affected by the local MSmooth to match the new size of the subdivided polygons.
14) The new polygons that we've created do not have an appropriate smoothing group. They aren't smooth as the others: