Hello @Alexandra_FOURNIER 
and welcome to the community!
Thanks for this tip 
— indeed, in SUIVI, the display order of columns and rows in a Kanban is directly based on the order of values in the attribute used for grouping. So, to reorder a Kanban (including 2-level ones), you just need to reorder the values in the settings of the relevant attribute.
Useful addition: when the need is rather to reverse the order only in the view (without impacting the “global” order of the list), we have precisely added a row sorting option in the Kanban view for groupings based on a Rating type attribute (typical case: 1→5 prioritization matrix). Details + screenshot in this thread: “Rating and KANBAN view”.
And for those building an Impact x Priority matrix, there’s also a “workaround” tip based on the Matrix view (super practical for prioritization): “Tip: use the Matrix view to build a prioritization matrix”.
Thanks again for sharing — feel free to post other Tips & Tricks 