Hi,
1. You can link a missing scene to other scenes using the "Set Scene Link" button in the bottom right.
2. You can set ending scenes by tapping the "Set Scene Link" and clicking the "No link, end here" option.
Please refer to the links below for more detailed information.
For links: https://help-iphone.playspinoff.com/links
For ending scenes: https://help-iphone.playspinoff.com/ending-scenes
Thank you!