If you right-click a program on the Windows 7 taskbar, a box pops up with a list of actions. This is the “jump list” for the program. If your app stores history or “recent items”, you can right-click an item and pin it.
You may notice that there is a limit to the total number of items in the “recent” and “pinned” lists. If you start pinning things and reach this limit, you won’t see the recent items anymore. For me, I was running into this limit at 15 items in the pinned list.
It turns out that the number of items allowed in the list is determined by the height of your Start Menu (for some reason). To increase the number of items, increase the height of the Start Menu. You can do this by right-clicking the Start Menu and choosing “Properties”, and then the “Customize” button. Increase the “number of recent programs to display” to make the Start Menu taller.
Once this is done, you can add more items to the “pinned” section of the jump list. If you pin more items and then go back and reduce the height of the Start Menu, the pinned items will remain (but you won’t be able to add any more without repeating this trick).