You do not put a special value into the Assignee field when creating an issue. The Groovy script is wired through the Assignee field definition, not as a value typed into the field itself.

How to connect your script

1. Go to Administration → Issue Setting → Custom Fields (or the project's issue field settings if they override the global ones).
2. Edit the Assignee / Assignees field.
3. Set Default Value to Evaluate script to get default value.
4. Select your script by its Name — from your screenshot that is Assign Questions to Junior Mechanic.

After that, when someone opens the new-issue form, OneDev evaluates the script and uses the return value as the default assignee. The script should return a user login name (juniormechanic in your example). If the field allows multiple values, return a string or a list of login names.

Docs:

• Scripting
• Default Assignee

Notes on your script

• The Can Be Used By Jobs / Workspace Specs toggles only restrict CI/workspace use. They are not required for issue field default values.
• Without an else branch, Type/Priority combinations that do not match return null and leave Assignee empty (Robin’s example returns another login in that case). Add an else if you want a fallback assignee.

If this clears things up, we can close the issue; otherwise say what is still unclear and we can escalate to @robin.

Amazing

Answered by wh