I didn't bring it up again because I found several (old) messages, some from Autodesk, telling it was very complex and so not implemented.
I found something in VBA, using a transform matrix like :
(XScale 0)
( 0 YScale)
This work to move all points in a drawing sketch, so :
-for lines it's ok
-for circles it move the center, just modify the radius after.
-for arcs it move start, center and end points. The problem is when one of these points move, the other too... There is a function "oSketch.SketchArcs.Item(1).Geometry.GetArcData" and "oSketch.SketchArcs.Item(1).Geometry.PutArcData", but I can't get it to work. I can get the datas (center, radius, start point, sweep angle), edit them, but I can't send back the new datas... any idea welcome ^^.
-for other items : not tested...
Here's the code, to test it create a drawing with a sketch containing only lines. The sketch will be sketched with a factor of 0.5 from the origin. (This code only work with lines)
Sub test_geo()
Dim oDoc As DrawingDocument
Dim oSketches As DrawingSketches
Dim oSketch As DrawingSketch
Dim oTG As TransientGeometry
Dim oSketchPoints As SketchPoints
Dim oSketchPoint As SketchPoint
Dim oScaleMatrix As Matrix2d
Set oDoc = ThisApplication.ActiveDocument
Set oSketches = oDoc.ActiveSheet.Sketches
Set oTG = ThisApplication.TransientGeometry
'Define the matrix
Set oScaleMatrix = oTG.CreateMatrix2d
oScaleMatrix.Cell(1, 1) = 0.5
oScaleMatrix.Cell(1, 2) = 0
oScaleMatrix.Cell(2, 1) = 0
oScaleMatrix.Cell(2, 2) = 0.5
'Select the first sketch, select points and edit the sketch
Set oSketch = oSketches(1)
Set oSketchPoints = oSketch.SketchPoints
oSketch.Edit
'For each point, apply the matrix to transform it then move it to the new coordinates
For Each oSketchPoint In oSketchPoints
Set p = oTG.CreatePoint2d(oSketchPoint.Geometry.X, oSketchPoint.Geometry.Y)
Call p.TransformBy(oScaleMatrix)
Call oSketchPoint.MoveTo(p)
Next oSketchPoint
oSketch.ExitEdit
End Sub