Is there a button to press that will lock in a rotate shape function to 90 degrees so the lines easily come out looking straight?

And there is a third option, which is to type the rotation angle into the Angle (labelled "A°") box of the Position toolbar, e.g 90, 270 etc, and hit Enter.  Note that this option is only available for single selections, i.e. a single line, symbol or group.

Kind regards,
Rob Robinson
Stardraw.com