As mentioned by Kate when a tenant is federated and directory lookup is enabled these users will automatically show up when assigning tasks, no need to bulk add. Also when they are assigned a task they are automatically on-boarded to NWC and will receive a login request.
We have 100000 users and we have AAD groups to handle different permission level and want to use those groups in our NAC. This is impossible for us to add thousands of users one by one in our NAC
I have a similar need, I have NWC with AD Federation. However without adding users manually I couldn't assign tasks to those users. Is there is a way to bulk upload the users? we have 500 users who would use the system.