Hi Romain,
I believe you're after the 'time-series export':
If you choose the Excel format, a new worksheet will be created for each selection. If you choose the CSV format, a new csv file will be created for each selection.
In both cases, the data will be shown as a time-series, with the first column as the time elapsed, and then each selected channel, with a value for each time-resolved measurement.
Is that what you were thinking of?
-Bence