Login Name in the record in Unifier

Dears,

Scenario

In Unifier, we have kept all policies assignments in the workflow, when each user accepts a task needs to capture all login user names based on the assignees for the step in the form. We tried doing the constant auto-population for the user picker, but it's not working.

Any alternate solution to get the multiple user's login names whenever the user accepts the record and should change dynamically.

Note: The step in which we need the login names is in between the workflow, it is not the creation step.