Sub Test()
Dim s As Shape
    For Each s In ActivePage.Shapes
    If s.Type = cdrCurveShape Then
    s.Curve.Nodes.All.Smoothen 20
    End If
    Next s
End Sub

https://community.coreldraw.com/sdk/api/draw/18/m/noderange.smoothen

    Dim OrigSelection As ShapeRange
    Set OrigSelection = ActiveSelectionRange
    Dim s1 As Shape