Use Up and Down arrow key to move keyframes up and down in graph editor

[Cubouse]

Detailed description of your suggestion

It's possible to click and drag keyframes in the Graph editor to change the chosen axis' value.

I wish that we could press the Up and Down arrow keys to do the same thing, as dragging the keyframes can be a little difficult to do without moving the keyframes left or right, and finely controlling the value can be hampered by the graph view scaling vertically to adjust for the value change.

Holding the key down would repeat the value change in increments.
Holding the modifier keys would modify the value change (Shift = 0.5, Ctrl = 0.1, etc)