First off, click the rendering menu up top, then select render and when the box opens go to the bottom and in the second line where it says Material Editor, unlock the padlock and set that line to Default Scanline Renderer. Then you little bubbles won't be blacked out like in your screenshot above. (see attachment 1 below)
Now to answer your question.
When you click the first little ball, and where it says standard right below it, click it and choose multi. (see screenshot 2 below)
When it asks, 'do you want to keep the original material?' choose yes if you already had a material setup in that ball and it will make it a 'sub/material'.
Try it out, you will see what I mean.
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