[palosanto]

You can do this already.

Long press a song in the setlist, choose "Edit Song" and set it's duration (at bottom of page)
Repeat for all other songs in the setlist.

In Settings/Library Settings check "Show Setlist duration".

I see there is "Calculate Setlist Duration Using Audio Files"; I'm guessing that you could check this and only adding durations for any files that don't have an audio track.

Note: You don't have to set all durations immediately, just those you need to use (the Setlist editor will say something like "55:02 mins  (21/23)" meaning that 2 songs don't have a duration specified)

Geoff

Geoff,
Just found this thread and I have a question:
Sometimes even if I have an audio track attached, I might play it faster or slower and that's the duration that I want to use so I tried overwriting the automatic duration   
but the total setlist duration doesn't change so it seems to ignore the new duration that I entered manually and still uses the audio track even though the duration field shows the one that I entered manually.

Is this normal or should the total set duration be updated?

Also, is there a way to filter what pieces don't have a duration so that I can enter it?
Thanks,
Juan