I could find this other answer which will probably help you: https://answers.atlassian.com/questions/50446/crowd-is-it-possible-to-bulk-add-a-user-to-several-groups
In other words, importing users from CSV should do the trick.
Hi there Community! My name is Serhat Can and I’m a Technical Evangelist for Atlassian with a focus on Opsgenie, as well as an AWS Hero and DevOps Days Core Organizer. I began my care...
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events