Many operations are performed through the sound font tree by right clicking on an item in the tree, which pops a menu. The options on the menu depend on which item was clicked.
Selections currently are only useful for pasting zones or deleting items.
This same procedure can be applied to Presets using Instruments as zones. The sample viewer is used to change loop points for samples and instrument zones. The distance you move the mouse from the original point of your click determines the speed in which the view zooms. If you then move the mouse to the other side of the line the view will unzoom. The default values are 32 and 8 samples for minimum loop and padding sizes respectively.