As explained in the scrapbook , in 2.0 it will be possible to drag one or several elements and to constrain the drag vertically or horizontally.
The current implementation uses Ctrl + drag and shift + Drag.
Shift is already used to select a range. Shift + click on a note or rest will select the rest with a blue rectangle. For a full measure rest, it will select the full measure. Ctrl is also used to select several elements.
Other software such as finale, use Shift only for this feature, and decide on the direction depending on the mouse move. The advantage is to save one keyboard shortcut, one less to remember as well. Shift being used for range, I wonder if it should be use for only one object. Shift click on one object could work as a single select, shift + click on another one would create the range selection.
Moving several elements with this proposal would use "Ctrl + Shift + Drag", the same shortcut than "drag+clone" but this feature will not work on several objects.