Version 4.0 introduced the ability to select from a list of layouts when viewing a show, and remembered the last layout you selected. But most layouts are sized for landscape or portrait orientation, so when you changed your device orientation, you also had to select a different layout.
Starting with version 4.1, the app now remembers the last layout you used in each orientation. So you can rotate to portrait orientation and select your preferred layout for that orientation, then rotate to landscape orientation and select your preferred layout for that orientation. Then whenever you rotate your device, Set List Maker will switch between the two orientations automatically.
(The BandHelper app works the same way.)