Constrain the circle components LenX and LenY in the Dynamic Components Attribute panel by formula.
And derive the position from the rectangle component.
Fredoscale is a solution. But I can not use it, because in my model there are many pieces (the rectangles of my post) whose lenghts are calculated. Changing all of them with a plugin would be slow.
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Thank you Mike,
Your solution works even if I make copies of the nested component.
I wish I posted last monday; I would have saved a lot of work.