do you know how can I connect a folder as an output for several recipes in the flow?
If I select a folder for a recipe, DSS does not allow me to link this folder for another recipe in the flow
Indeed that pattern is not possible. This is by design to avoid conflicts/concurrency issues when writing from different recipes to the same output.
In DSS 7.0 (new!) we have released a new recipe to "Merge folders": https://doc.dataiku.com/dss/latest/release_notes/7.0.html#merge-folders-recipe
This way you could have different recipes writing to different output folders, and then a Merge folder recipe to merge all folders to a new one.
Hope it helps,