Xcode kind of just want us to have ONE storyboard in a project.
But that is difficult for a team to work on because it is almost impossible to resolve any merge conflicts for storyboard (utterly complex XML).
There are 2 ways.
Pass along a banana
Yeah. Really. Literally.
Have only 1 person to edit the story at any one time.
He who can edit holds the banana. Or any other token.
Multiple Storyboards
An improve to the banana system is to have multiple bananas. Or multiple tokens. So more monkeys developers can work on it at the same time.
This requires you to decompose your storyboard into modules.
Then make sure of RBStoryboardLink to link the storyboards together.
What is RBStoryboardLink? It links Storyboard A to Storyboard B by placing a pseudo view controller in A, with attributes saying what storyboard name and scene name it links to. The magic comes from their custom segues.
Unwind segues works too.