In JIRA it is possible to copy users from a group to another group using the user picker in Bulk edit group members
This is not possible in Crowd.
It would be very useful to select add users to a group in bulk based on another group
In a KB article of a similar resuest a workaround is described using SQL statements and csv imports: https://confluence.atlassian.com/crowdkb/how-to-create-a-copy-of-a-group-membership-to-a-new-group-in-crowd-732269562.html
This is a very time consuming workaround and only worth it when copying large amount of users.
Not every Crowd admin has access to the database to run SQL queries and to the application server to place a csv file on the correct location
Please consider this request