Merge segments from different Hierarchy model

Dear all, I am wondering how to merge segments of different model hierarchy. I did not pay attention at the beginning but I created different “segments” from the same object I want to segment. In other words, the same object A has two similar segments.Please see below the image.
The logical operator effect can merge two segments from the same hierarchymodel but also from different models? Sorry If it is not clear.

Finally, I would be very grateful to know the differences between the segments into the “Segmentation” and the “ModelHierarchy” nodes.

Thanks a lot for your help

You can find a diagram that demonstrates the role of the different data types such as segmentation and model:
Basically model hierarchy nodes are simple folders.

You can convert these model hierarchies to segmentations (and back) by right-clicking the respective nodes. Once you have the segmentations, you can drag&drop segments between segmentations that then you can merge (I guess you want to use union) with the logical operators.

Thank you very much for this information
Best regards