GENERAL
Ctrl + S -> Save
Ctrl + Z -> Undo
Ctrl + Y -> Redo
PLACING OBJECTS
Hold Ctrl -> Snap to grid
SINGLE OBJECT PLACEMENT MODE ONLY
Hold left mouse + R -> Rotate
Hold left mouse + E -> Scale
SELECTED OBJECT
Ctrl + D -> Duplicate
Ctrl + L -> Toggle Light
Ctrl + H -> Toggle Hidden
CHANGING PIVOT POINTS (for door rotations etc.)
Select object + hold shit + drag move icon