Hi Antonio Györög,
You can select the objects in the named selection using "Select item in group" as shown below.
I am not sure if understand your query correctly, but you can edit the origin for the coordinate system(if you don't want it at the centroid of geometry you defined using the named selection) by changing the coordinate values as shown in the image. Can you share some images of the issue you are facing, so that it will be easy to understand and help?
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