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The feature allows you to create Scheduled Issues that has multiple Assignees (1)
The way it actually works is that it uses Jira project groups. Once Group Assignee on SI is selected then on execution there will be created JIra ticket separately (2) for each user (1) from the group:
Execution History
At Execution History of Scheduled Issue that has Group Assignee you also have available preview of current status of Jira tickets created with Scheduled Issue
Scheduled Issues Table
At Scheduled issues table you can differentiate Group and regular assignee by checking presence of a
flag (1)