Hello @BendegzHegedus
Your challenge output results to be a ‘nested hierarchy in column header’ table. And as you pointed out, it’s somehow based in grouping: then the best choice is a Group Loop node and some column name rearrangement.
What is conceptually missed in your description is an output ‘row sense’ column, further than a row ID. In this case could be something like measurement_round …
Your workflow could be something like this; considering the data is sorted by time:
BR
PS.- Be aware that once your dada is arranged in this way, it couldn’t be usable for some analysis or visualizations, and return it back to original shape can require complex back transformations.