On Windows, pressing "0" on the number pad when the song is stopped will return the cursor to where ever it was when you pressed start. Even if your song stars on bar 5, if there cursor was at bar 5 when you pressed start, pressing 0 on the num pad when the song is stopped will return the cursor to bar 5. This is a preset key command on Windows. You don't have to create it.
I don't know the key command for this on MacOS, but there must be one.