You can group sketch geometry together by creating a SketchBlockDefinition out of them using the "Create Block" command:
If you have SketchBlock's (instances of SketchBlockDefinition) in your Sketch then through the UI you can constrain them together without creating any additional geometry in the SketchBlock's definition (SketchBlockDefinition) - e.g. using the midpoint of one of the lines of the SketchBlock:
You can work around that by creating the constrained SketchPoint inside the SketchBlockDefinition, and use the representation of that point in the Sketch to add further constraints. Each object in the definition will be represented by a sketch object inside the sketch where you placed the SketchBlock. You can find out which object in the sketch is representing a given object from the SketchBlockDefinition by using the SketchBlock.GetObject() function.
FYI: the first SketchPoint in the SketchBlockDefinition is always the insertion point:
Sub ConstrainBlockLine() Dim oPartDoc As PartDocument Dim oSketchLine As SketchLine Dim oMiddlePoint1 As SketchPoint Dim oMiddlePoint2 As SketchPoint Dim oTG As TransientGeometry Dim oSketch As PlanarSketch Dim oSketchBlock1 As SketchBlock Dim oSketchBlock2 As SketchBlock Dim oSketchBlockDef As SketchBlockDefinition Set oPartDoc = ThisApplication.ActiveDocument Set oTG = ThisApplication.TransientGeometry Set oSketch = oPartDoc.ComponentDefinition.Sketches(1) Set oSketchBlock1 = oSketch.SketchBlocks.Item(1) Set oSketchBlock2 = oSketch.SketchBlocks.Item(2) Set oSketchBlockDef = oSketchBlock1.Definition 'edit Sketch Call oSketch.Edit 'edit SketchBlock Call oSketchBlock1.Edit Dim oMiddlePointNative1 As SketchPoint Set oMiddlePointNative1 = oSketchBlockDef.SketchPoints.Add(oTG.CreatePoint2d(0, 0), False) Set oSketchLine = oSketchBlockDef.SketchLines(1) Call oSketchBlockDef.GeometricConstraints.AddMidpoint(oMiddlePointNative1, oSketchLine) Dim oMiddlePointNative2 As SketchPoint Set oMiddlePointNative2 = oSketchBlockDef.SketchPoints.Add(oTG.CreatePoint2d(0, 0), False) Set oSketchLine = oSketchBlockDef.SketchLines(3) Call oSketchBlockDef.GeometricConstraints.AddMidpoint(oMiddlePointNative2, oSketchLine) Call oSketchBlock1.ExitEdit(kExitToPrevious) Set oMiddlePoint1 = oSketchBlock1.GetObject(oMiddlePointNative1) Set oMiddlePoint2 = oSketchBlock2.GetObject(oMiddlePointNative2) Call oSketch.GeometricConstraints.AddCoincident(oMiddlePoint1, oMiddlePoint2) Call oSketch.ExitEdit End Sub