Choose layouts for each item (or for all) to quickly updated how many lines are on each slide.
Tap the settings icon to the right of any item
This is to edit the layout for each item separately. (To update the layout for all items at once, use the general settings icon at the lower right of the iPad or the upper right on the iPhone.)
Slides are updated.
When you tap to choose a new layout, it is selected and your slides are updated in the background. Sequence sections (Verse, Chorus, etc.) are always started on new slides.
Layouts & Slide Breaks
When you choose a new layout, the slide breaks for each section are updated. Every layout can have customized slide breaks that are saved with the layout. For example, if you have a 4-line layout that you have customized to have 3 lines on a slide just for the verse, that customization is saved with that layout. So if you switch to a 2-line layout and then later back to the 4-line layout, the slide breaks you had previously customized for the 4-line layout will be retained.
Check out this lesson on Editing Slide Breaks