Hi Kenneth, The multibox it self have search option. Select dropdown and type on it. Automatically the search box was enabled on top of the multibox. If you want change the search mode Presentation --> Select Field --> Advanced
We are struggeling with the same problem. I even connected a keyboard cover to my iPad. And still no success. The only solution I see is to have this field NOT in the multibox but as a separate field. Then it is possible to key text for selection.
As a general rule, multiboxes are avoided when designing for an iPad. They are not easy to navigate using your finger and they are usually replaced with search objects because of the problem you are encountering. Some android tablets will allow you to swipe up and down the list without using the slider.
Have a look on the forum for Best practices for iPads and you will find more suggestions on how to design your app for iPad use.
You can create a workaround by placing a searchbox above your Multibox which is on conditional show. So only when you select one of the 10 items, the search box will appear and will let the iPad user search for the 500+ items.