On the XT, I haven't found a feature that allows brightness or volume ont he right hand side of the screen. It used to be there on many earlier Zumos, but not on the XT. But (I don't have an XT2) but these are the palces that you might want to look.
There are certain items that you can display down the right hand side of a Landscape view map.
eg
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View Map ->3 dot menu bottom right -> 3 bar menu top left.
Tap one of the existing icons, it will disappear and be replaced with a plus + icon. Tap that and you can add any of :
Map Orientation, Map Layers, Skip, Garmin Powerswitch, Stop, Edit Route, Mute.
Any three icons can be displayed alongside the map.
OR
View Map->3 dot menu, bottom right
This allows you to view Trip data - which displays and additional 3 rectangles which can show all sorts of data about your trip.
OR
Right hand side mini apps such as Music Player, Traffic, Track Recorder, Weather, Up Ahead, Towns Ahead, Elevation, Turns, Phone, Report Safety Camera, Photo Live.
Also on the XT it is possible to create shortcut for favourite searches, categories or favourites. These appear as additional icons in the Where To? page. But I have not found the ability to add links to other apps.