In Collaborations, there is currently a "Remove all" option for Collaborations with users. Including an "Add all" option would make the process much easier, while also eliminating the possibility of omission errors.
Imagine: You teach a class of over 100 students and you wish you take the wonderfully updated Collaborations tool for a spin. Then you realize that to add your entire class to a Google Docs, Slides, or Sheets collaboration means you must add each individual student one at a time. That's a lot of clicks and a recipe for inevitable emails from students you accidentally skipped over. Using an "Add all" option when creating a Collaboration would eliminate both of these burdens.