FunctionKeyNotes
MoveSpace
RotateShift + Space
Zoom toolCtrl + SpaceBetter than +/- zoom
Zoom inCtrl + +
Zoom outCtrl + -
Reset RotationAlt + R
Reset ViewAlt + G
Flip Horizontal´
Hide Side MenusTab
FullscreenTab

Brushes

FunctionKeyNotes
Brush SizeCtrl + Alt
Switch ColorsX
Reset ColorsD
Opacity 10%-100%1-0
Make your current brush to eraserC
Straight lineShift
Cycle through PencilsP
Cycle through BrushesB
AirbrushA
BlendJ
EraserEHold and let go to automatically go back to the last used brush
EyedropperAlt

Other

FunctionKeyNotes
MoveK
TransformCtrl + T
Select LayerCtrl + Shift
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SelectionM
Invert selectionCtrl + Shift + I
Remove SelectionStrg + D
Auto SelectW
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Edit Vector LineO

Pen Setup and Extra Info

My front pen button changes brush size (Ctrl + Alt) while my back button is a right click, so I can get to hidden menu elements.

Some functions like rotate and move do not have their own hotkey, to give these functions a hotkey one must assign the tools via the Modifier Key Settings menu, the desired hotkey