User cannot see search icon when “Administration” tab is opened in Developer, therefore cannot perform a search for configuration objects, despite having "Use Search Editor" privilege.
Configuration objects are not Project-specific, and the needed privilege "Use Search Editor" granted via Security role only works for Project-specific objects.
The "Use Search Editor" privilege has to be granted directly to the user or user group. This way the privilege will also affect non-project-specific objects, such as configuration objects.