A switch material can contain several materials but only one of them is visible at the same time. Create switch materials the same way you create MultiPass or layered materials -either drag within the render view with select Create Switch Material selected or drag within the material preview list. To assign several material variants on creation, select them and then select Create Switch from Selection from the context menu.
If a switch material is selected, all the material variants are present within the Switch Choice section below the material preview list. Click a child material to open its properties. Double-click a child material to activate it.