I wonder this since there is a max amount of space there. If I install multiple lenses, will it slow down the Dash menu, can I horizontal scroll to see other lenses available?
In Ubuntu 11.10 and 12.04, there is no limit to the number of lenses that can be installed. However, once the amount lens icons exceed the available width, it is not possible to see or select them with the mouse. They can, however, be navigated to using the keyboard (TAB in 11.10, SHIFT + TAB in 12.04). There is no horizontal scroll available in the lens bar.