Inventoids has a post on a neat way to make those "inverted tabs".
"The side view shows the general effect. These inverted tabs are very
easy for your thumb to locate. I’ve used them to split one notebook
into 6 separate sections, for separate projects, all along the vertical
side. For a more sophisticated setup a mix of tabs on the top, bottom
and edge could separate 3 different types of sections, with individual
sub sections along the length of the edge…"
Share your favorite Moleskine hacks/mods.