Images Bbox object detection + Relations

I want to create relations between bboxes of two images. Since the relation is based on the same labels I want to use just one RectangleLabel object for each label so I can use them in both images. So far I have this layout (as you can see I need to duplicate the labels) :

I tried this, but it didn’t workout (It doesn’t allow me to mark the bboxes):

<View style="width: 49%; margin-right: 1.99%">
  <RectangleLabels name="class-left" toName="img-left,img-right">
	<Label value="Avion" background="green"/>
    <Label value="Car" background="red"/>
  </RectangleLabels>
  <Image name="img-left" value="$image1"/>
  <Image name="img-right" value="$image2"/>
</View>