Let me provide a bit more detail.
This would be a Create Workflow with the “Bulk Import Usage” enabled. By doing this you can upload a CSV file to create Identity profiles for the users, and then use the aforementioned API endpoint in my previous comment to Create a Collaboration account for them. This Bulk Import functionality allows you to map the CSV headers to NERM attributes. The system essentially processes each row separately, so if one row failed for any reason it would still process the other records/rows.
Documentation for how/what Bulk Import workflows can be found here → New Capability: CSV Profile Import for Business Users!
Hope this clears it up!