Each closed face creates one object per selected surface. Connected islands combines touching selected geometry. Loose edges remain in place in face mode.
Matching faces share one definition, including the original. Touching or separate faces both work. Geometry, orientation and materials must match; nested geometry stays unique.
Live name example
In preview, Enter creates all and R reverses numbering. Click a shape to review matching shapes. Pick Axis Point uses the same relative location on every component; arrow keys lock the axes.