Features used to implement the example

• Set a field as a function of other fields

Example: Unassign an issue when assigned to project leader

I'm trying to clear assignee field for one issue type in project with auto-assign to lead. I've create post-function in create transition but it doesn't allow to clear field. Then i set value to real-user name function reassigns issue to user, then i try to set value to "None" or "Unassigned" it leaves project lead as assignee

I have just released Jira Workflow Toolbox 2.0.22 which has the extra functionality of unassigning issues when writing "Unassigned" (case unsensible) into virtual field "Assignee".