Constrain tool movement with keyboard modifiers

• a face or on section plane

(don't think I missed one, but just in case, etc.)

But even then SU snaps to relevant geometry with the restrictions as mentioned above. You cannot turn off 'snapping to.'

First, to move in any non axial direction: draw a guide that determines the desired direction.

So, draw a diagonal guide in the rectangle and use it to constraing the moving vertex to it by holding down [Shift].

Any guide through the vertex to be moved will give you something to "slide along" while holding down [Shift].

If you work with moving preselected geometry (not just hovering over that vertex to move it) the guide may even be somewhere else beside the geometry. First and second click on the guide ensure the geometry to slide in the right direction.

Start moving, then press the appropriate arrow key to lock movement along an axis.

(add imagery)

Use Shift + arrow keys to constrain movement along a selected axis while using other geometry to infer from.

(add imagery)