Why is the Study Selector missing from Study Info --> Studies but is still available on the Study Site and Study Country sub-tabs?
This is working as designed. Since the Studies sub-tab displays general information about studies, the search bar at the top of the page can be used in place of the Study Selector. The Study Site and Study Country show detailed information regarding studies requiring the use of the Study Selector.
Vault eTMF Documentation: Using the Study Selector (eTMF)