After adding a new zone to a layout in zone.ini, the change is not visible when editing an object with that layout attribute.
The only workaround is to choose a different layout (loosing any block costumization), and choose the original layout once more.
- Add a new zone to a layout in used (like the homepage)
- Clear caches, edit the content object with that layout
- The new zone is not displayed, unless a different layout is selected.