"This pc"

Why I don't see "network" drives in "This pc"
Is there a box ticked somewhere?

Do you mean network drives you have mapped a drive letter to, or something else?

In two words, I don't see my "box" on DO for family use in order to avoid USB keys...but on W10 I see it
view the photo
ce pc

In Opus, the options for the This PC (aka "Computer") folder are here: Preferences / Folders / Virtual Folders.

That looks like it's just a shortcut to a network drive, though, stored in a C:\Utilisateurs folder. That wouldn't automatically appear in This PC, in Opus or File Explorer.