Nudge Position Up ⌃⌥⌘↑
Move the selected item up. I am not sure of the exact distance the symbol is moved, but it appears that it can be +/- 999 steps. Same increments for left and right. The symbol information is in the Event Inspector box.
The information in the symbol inspector includes Symbol (a number), Staff, Vertical Position, Horizontal Position.
Using key commands: You can use key commands to move any score symbol that can be positioned independently of notes or staffs, as well as text events and chord symbols. These functions don’t alter the bar position of the affected symbols and text events. They alter the Horizontal Position and Vertical Position parameters by ±1.