Ctrl + A = Select All Nodes
Ctrl + S = Save
Ctrl + Shift + S = Save As
Ctrl + Shift + O = Open
Ctrl + Shift + N = New
Alt + F4 = Exit
Ctrl + Shift + Alt + P = Export to PNG
Ctrl + Shift + Alt + J = Export to JPEG
Ctrl + Z = Undo
Ctrl + Y = Redo
Ctrl + N = Add Node
Ctrl + LMB on Canvas = Start Select
Ctrl + LMB on Connector = Create Loop
LMB on Node = Select one Node
Ctrl + LMB on Node = Select/UnSelect Node 
Ctrl + LMB on Transition = Select/UnSelect Transition
Shift + LMB on Transition = Multiple selection
LMB on Connector = Start create Connect
Alt + LMB on Connector = Move Connector in Node
Alt + LMB on Canvas = Start Cut
Delete = Delete Selected Elements
C + Delete = Delete Selected Connector
N + Delete = Delete Selected Nodes