Assuming you are using the insert row action on the Sheet node, I believe it currently reads from the header row (in your case Densité, Observations and Tamis) and that’s what it recognizes as the columns.
Do you have a fix number of Tamis columns? If so, one thing you could try is having a top header hidden row with all the necessary columns so you’d be able to pick them in the manual column select on the node’s options: