Straighten Preferences

Doubleclicking the Straighten tool in the toolbox (or pressing the Enter key when the tool is selected) will bring up its preferences dialog:

Straighten Preferences

1. Snap Tolerance

The tolerance for the cursor when snapping to existing paths, in pixels.

2. Ignore Constrain Angle

When enabled, the constrain angle is ignored when straightening the segment (i.e., it will always be parallel to an artboard edge).

3. Informational area

Shows a brief description of each preference control when the cursor is being hovered over it.