This is currently not natively possible, but there may be a feature request for it. If not, you may create a feature request for it.
However, you can mimic this behavior by using action rules. Set up an action rule for each tech as follows:
- Evaluate criteria on all ticket updates.
- Apply action only on ticket creation.
- Criteria: Subject contains assign:jd
- Action: Assign to Tech John Doe
Unfortunately, there is not a way that I can find to remove the "assign:jd" from the subject except manually.