I appreciate your time and your efforts, but that really doesn't work at all for what I want to have happen on my site, and really wasn't what I needed or meant at all, though I appreciate you taking the time to respond.
I was never interested in having another menu or having sub items, my original menu's just fine.
What I wanted was all the menu items appearing in a straight horizontal line one after the other at the top of the site as you can see in the images I linked to from the theme demo.
Others are asking the same question in other threads here:
I got an answer several days ago by asking Caroline (the original creator of the Sketch theme) on the original post that announced the new Sketch theme here:
(See the comments on that post for anybody that might be looking for an answer to the same question that I had, and it seems that others are having too.)
According to the answer I got from Caroline, it seems that the menu items will only appear in a straight line at the top of the site if your screen size is bigger than 1280 pixels, and for anything smaller than 1280 the only way to get them to appear in a straight line is with the Custom Design package.
However I don't want to and can't (and wouldn't even if I could) pay for the Custom Design package (and wouldn't be able to code what I want in CSS anyway even if I did have the Custom Design package), and I have a smaller screen size it seems, so it seems my menu items will always just appear behind a menu button instead of in a straight line, unless I look at my site on a computer with a larger screen, unfortunately.