If you don't need to see your song list while playing your songs, the easiest solution here is to use a layout like More Buttons or Overlapping Buttons and show the larger document for all songs. Then use a two-fingered tap to show the song list between songs.
But if you do need to see your song list while playing your songs, but on some songs you want to trade that space for a larger document, you could try this:
1) Select two layouts you want to switch between, like Split View and More Buttons. Then go to the Layouts list and edit the details for all the layouts above the gray line, except those two, and turn off the Active switch.
2) Edit the details for those two layouts and set Next Layout to Three-Fingered Tap.
3) For the layout that shows the larger document, edit the song list and turn off Show Initially.
Now view a show with the split view layout. When you want the document larger, tap with three fingers to switch to the other layout. When you're done, tap with three fingers to switch back.
The only downside to this is that most functions will reset when you change layouts, like auto-scrolling, tempo playback, etc. So you'll need to decide that you want the larger document before starting the song if you're using functions like that. (The recording can keep playing if you turn on Settings > Audio & MIDI > Continue Audio When Changing Songs.)