For those who don't know, the "Pad Only" area simply houses apps that are tagged as pad-only by users -- you can do so by tapping and holding an app icon in the drawer, followed by dragging it to the "Add Pad-only Tag" button in the top-right corner.
If you have a really large project, with hundreds of clips, pressing (and holding) shift will present a zoomed-out view, where each pad now represents an 8 x 8 section of a project, letting you quickly jump about to different parts of the session.