I was about to ask for help resolving what I thought was my own menu padding problem when, for whatever reason, I pulled up Chrome’s “Inspect Element” [Ctrl + Shft + I]. The diagram under the “Computed” tab clearly showed it wasn’t the nav bar padding but my Page’s unique “Feature Image” top margin (just below the nav bar) that was the issue–it was set to 30px, which would make sense if I didn’t intend it to replace my header image. So, a search under the “Elements” tab led to this string which I copy-pasted into Additional CSS and set to 0px:
.separate-containers .page-header-image, .separate-containers .page-header-content {
margin-top: 30px;
}