[Geoff Bacon]

There are multiple ways to do this

Suggest you long press the Setlist name and select Copy (at the top)
Adjust the displayed name (add "Part 2" to it?)
Edit this new list and long press the first song until a check box appears
Select all the next 15 songs and Delete

Edit the original list by deleting the last 16 songs
(rename list to have a "Part 1"?)

Another way is to long press/select a group of songs and "..." (top right).
Select "Create set list from selected songs"
Edit the original list as above.

Geoff