The best replacement for storyboard is nib.

The best alternatives to storyboard are rated as following:
★★★★★  nib
★★★★★  xib
★★★★★  wireframe
★★★★★  script
★★★  script first
★★★  storyboard
★★  interface builder
★★  xib files
★  shot list
★  animatic
★  dispatchertimer
★  timeline
  screenplay
  mood board
  story board

Your alternative for storyboard is not listed? Suggest!
Speaking about storyboard, one probably shouldn't forget about xib.

Other search terms related to storyboard and their ratings are:
★★★★★ xib
★★★★ navigation controller
★★ segue
You have in mind a companion for storyboard and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of storyboard in all years. Click on graph for more.
storyboard
nib
xib