Possible noobery on my part but I’m not seeing that setting (old.lemmyworld)?

When I click on settings (top RHS of screen) I’m confronted with three pulldown menus and five tickboxes -none of which include that setting).

Edit: Just realised I’m on the syncforlemmy forum. Like I said complete nobbery on my part but I would like such a feature on the old.lemmy interface)