If you have to scroll to the see your entire Start menu, you're using it wrong.
This is, of course, exactly the same as the last three versions of Windows, so it shouldn't be a revelation. The only difference is that it looks different.
Pin anything you use all the time on the task bar, and remove them from Start. Remove other items you don't need to see every day. All apps are always available through keyboard search and via the All Apps option.
Oh, and if you want to add more items vertically, go to Start -> Settings -> Tiles -> Show more tiles.