1-6 - Modify scale (1 = default, 2048 x 2730px, 6 = maximum, 12288 x 16380px (very performance intensive, will take a long time to render))
F - Fit to current screen size
G - Toggle grain overlay
L - Toggle background grid lines
B - Cycle border sizes (0 -> 100 -> 200 -> 300px)
Updated