Hi Julien,
Welcome to Box Community and glad to help!
You can hide collaborators to prevent your collaborators from seeing the list of other collaborators in a particular folder. With only the Owner and Co-Owner who can do so.
To hide collaborators:
- Right-click the folder (or click the ellipsis (...)) to open the More Options menu.
- Click Settings to open Folder Settings.
- In the Privacy section, check the box next to Hide collaborators and their activity from non-owners.
To find out more, please visit this helpful article.
Hope it helps!