I want to resize the background of my element dynamically with the bounding box size of a text.

Unfortunately, with my approach, this is only working with geometries like the 2d text, because they give back a bounding box in its outputs.
When I want to test for multiple lines which are multiple elements, it would be nice to get the bounding box of a whole hierarchy, like from an axis node.
Is it possible to get it in another way?
thanks in advance
Leo