Unreal Engine 4.18
LMB Drag – move horizontally on the X Y plane.
MMB Drag – move on the viewing vertical plane (to the sides and up / down ).
RMB Drag – Rotate (Pan) the view without moving.
Alt + LMB Drag – Arc Rotate view
Alt + RMB Drag – Dolly In / Out view (move forward and back ward along viewing axis)
F – Frame Selection (Zoom Extents)