Revise behaviour of get_aggregated_panels, document behaviour and refactor if needed

[Eva C]

Description

get_aggregated_panels has some inconsistent behaviour. This method needs to be revised and the logic documented.

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[ChristianOertlin]

Can you describe the inconsistent behaviour that you have observed?

added to refinment for 19-06-2024

[Henrik Stranneheim]

Refactored here: #3383