Summary

Assignee field is not visible on 'Create Linked Issue' (functionality available for Business/Service Desk projects on JIRA 7 and above) screen even if unassigned issues are disabled on the instance. On the regular 'Create Issue' screen the field is show normally.

Steps to Reproduce

1. Go to General Configuration and turn off the option 'Allow Unassigned Issues'
2. Create a issue on a Business or Service Desk project. Note that the assignee field appears, if it has already been added to the respective create issue screen.
3. On the Issue View screen of the newly created issue, select More > Create Linked Issue
4. Note that the assignee field does not appear, even though it is theoretically a required field. The linked issue will use the default assignee for the project, however.

Work-around

This is not possible to add the Assignee field to the 'Create Linked Issue' screen. To have issues assigned to users other than the default it is required to manually edit the linked issue and change the assignee.