Even if the game engine is not the most recent, you should not get such a lag. On top of my head, you should scroll without any stack in selection, this will be faster. You can also scroll with the arrow keys, and as Cpt Orso says, you can click on the minimap for a 'big jump'.
You can also play with a smaller window, so there is a less to display at a time. Run the AGEsettings utility, or simply edit display.opt in settings (that's a text file) and give a window size of 1024x768 for example.
That said, you can also ask for guidance from the HelpDesk: email@example.com