box Plot : How to Add another field/box ?

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Good morning,
I am a newbie with this Data Plotly plugin.
I manage to represent (input layer: point shp layer) a box plot with the thematic id_classes in X axe (4=bare soils, 5=vegetation, 6=water) and in Y axe the NDVI vegetation index values. These values are those for the dry season. I would like now to be able to add to the right of each existing box the representation for each class_ID of the NDVI values this time for the wet season.
So each class_id would have a "pair" of boxes: 1 for the dry season and 1 for the wet season.
How can I do this? It's seems to be possible (an exemple seems to be given on the documentation .
Below my existing box plot :

Below the box plot of the documentation :

Thanks !