The Nintendo DSi theme splits items into pages with a maximum of 40 items per page. You can navigate through the pages using the and triggers.
Pressing on the leftmost page will take you to the first item on the page
Pressing on the rightmost page will take you to the last item on the page
The scrollbar at the bottom represents all of the items on a page so you can tap on it to quickly move to a specific location in the page.
If your triggers do not work, you can use SELECT + instead.
TWiLight Menu++ supports displaying custom photos on the top screen, just like the official Nintendo DSi Menu. However, rather than have it pull from the Nintendo DSi Camera application, you can place PNG images in sd:/_nds/TWiLightMenu/dsimenu/photos
If the image size is less than the maximum, it will be centered with black borders.
Pressing SELECT in the Nintendo DSi theme will bring up the DS Classic Menu by default. However, in the TWiLight Menu++ settings, you can change it to launch the SELECT Menu, a miniature menu embedded inside the theme itself. Here are the menu options for the SELECT Menu.