2026.2 and higher
Right-click (on a song title) > Duplicate
Alternatively click on a song title then either cmd + D or File > Duplicate or then click the Edit Pencil icon (top right) and choose Duplicate
(v2026.1 and lower use the Control key instead of the Command key)
When you duplicate a song, make sure you change something in the song like a chord or text, otherwise the duplicated song won't save because nothing has changed.