SketchUp Pro: Problem with Materials Trays

Hello, I have a very slight problem with the Materials Tray (see attached image). I created a new siding material (the one with blue highlight around it) in the top tray. I cannot seem to drag n’ drop it into the lower tray (currently showing my brick, cladding & siding textures). When I drag the texture from the top tray, it will not appear in the lower tray. I watched a YouTube vid where the guy was able to do this, so I’m a bit perplexed as to why I can’t repeat his steps. Any suggestions?

(The attached image may appear collapsed here, please click on it to expand it to see both trays.)


Check out the reply by DaveR on another post about this issue.

Which was a reply to @Joel_Cairo with the same question.

Ah, yup. Dave is right. I did ask this question before. My bad. I would delete this thread, but I see no option to do so.