(Re)Draw a straight line

1. enable SnapToObjects (Alt-Z), move line's rotation point to one of its ends
2. create a guideline, snap it to that same line's point, enable SnapToGuides (it's the default behaviour)
3. switch to rotate mode, grab the other end point of the line so that it is "snapped" (tick mark is shown) and rotate it so that the node snaps to the guideline

.....I've just thought that I need this a few times a week, so here's two macros to straighten such lines, but don't ask me how to use them, LOL

Sub StraightenLinesH()
   Dim sh As Shape, a#, x1#, y1#, x2#, y2#, x#, y#
   On Error Resume Next
   ActiveDocument.ReferencePoint = cdrCenter
   ActiveDocument.BeginCommandGroup "Straighten lines horizontally"
   
   For Each sh In ActiveSelection.Shapes.FindShapes(, cdrCurveShape)
      sh.GetPosition x, y
      With sh.Curve.Nodes
         .First.GetPosition x1, y1
         .Last.GetPosition x2, y2
      End With
      If y1 <> y2 Then
         If x1 = x2 Then a = -90 _
            Else a = CorelScriptTools.AngleConvert(2, 1, _
                        Atn((y2 - y1) / (x2 - x1)))
         sh.RotateEx -a, x, y
      End If
   Next
   
   ActiveDocument.EndCommandGroup
End Sub

Sub StraightenLinesV()
   Dim sh As Shape, a#, x1#, y1#, x2#, y2#, x#, y#
   On Error Resume Next
   ActiveDocument.ReferencePoint = cdrCenter
   ActiveDocument.BeginCommandGroup "Straighten lines vertically"
   
   For Each sh In ActiveSelection.Shapes.FindShapes(, cdrCurveShape)
      sh.GetPosition x, y
      With sh.Curve.Nodes
         .First.GetPosition x1, y1
         .Last.GetPosition x2, y2
      End With
      If x1 <> x2 Then
         If y1 = y2 Then a = 90 _
            Else a = CorelScriptTools.AngleConvert(2, 1, _
                        Atn((x2 - x1) / (y2 - y1)))
         sh.RotateEx a, x, y
      End If
   Next
   
   ActiveDocument.EndCommandGroup
End Sub

Another option is to turn on dynamic guides (alt+shift+d). With a little practice, you can straighten a line to 90 degrees with the nodeedit tool very quickly.

Regards,
Hendrik