Set Custom Slab Edge Angle and Edge Surface

Angle: Choose an angle (Vertical or Custom) for the slab edge. If you choose Custom, enter the desired angle value in the field at right.
Note: By default, the Surface material applied to a Slab edge derives from the Building Material assigned to the Slab. You can override all edge surfaces of the Slab, using the control in the Model Panel of Roof Settings. The Custom Edge Settings offers a further way to customize the surface of any one or more Slab Edges.
Surface: Click the Surface override button, then choose a custom surface for the slab edge(s).
If so, check the box at the bottom of Slab Settings (Apply changes to custom planes/edges too). If you do not check the box, your custom edge surfaces remain the way you set them.
Clicked Edge will apply the options you choose below (angle, surface) only to the edge you clicked when bringing up the pet palette.
Selected Polygon will apply the chosen options to the edges of the slab only or the edges of the hole only, depending on which one is selected.
All Edges will apply the chosen options to all edges of the slab as well as all edges of its holes. (If the selected slab has no holes, then Selected Polygon and All Edges have the same effect.)
To apply the customized values to the hole only, then choose Selected Polygon from the Apply On pop-up.