Draw two new axis lines, one representing horizontal and the other vertical on the selected point cloud (if snapping to the point cloud is required ensure "Line" is selected from the Point Clouds menu followed by highlighting the "Add" pencil icon):


Select both lines (horizontal first) highlighting them blue and select the "Align" icon.  The point cloud will transition relative to the new axis:


Note: Use Axis, Flip and Rotate to correct the orientation.  Select the Axis from the list: