The small screen on the Surface works well with 3 rows of tiles, but if you want to lose a little of the aesthetic to add a little to the efficiency there’s a simple tweak that will enable the 4th row. All you need to do is add one registry entry: HKLM/Software/Microsoft/Windows/CurrentVersion/Explorer and now add a new key: Scaling with a value of "MonitorSize"="12.1"
Deleting the entry reverts back.
On your RT just go to search and type ‘regedit’ and it will bring you to regedit.exe if you don’t know. Or you can do it this way:
1. open notepad
2. post following line:
Windows Registry Editor Version 5.00
3. save as a .reg file
4. import into regedit
5. restart surface
Apparently you can go even higher as some people have used 13.1 to get 5 rows. And in case you don’t know, if you are in the Metro home screen, turn the screen to portrait and go to the charms and then go to settings there will be a ‘Tile’ option available that lets you enable extra rows. If you apply this tweak then the default 6 (which the setting option changes to 7) can now go to 9.
Like all registry tweaks, do this at your own risk. We have no liability…yadda yadda
You can read more here on XDA.