OK. Now I actually read your old thread. My other advice still stands because if you address the feelings you're having it won't matter what your boss thinks... And being happier in your current position is actually going to put the manager at ease so they're comfortable promoting to the next level. Sucks but that's how companies work.

Tactically I would sit down with your supervisor and discuss what's troubling you, what you're trying to get out of your career and why you're not fulfilled. Then ask them what's expected of you to get promoted: is it time on the job, is it leadership on the team, is it technical achievement? What will make me stand out in this company on this team? There may be details that you don't know that are blocking your progress. If you aren't satisfied with the answers then ask around to see if other teams in that company are recruiting engineers. Don't make it a competition with your boss. Stay humble. Try to be positive about what your boss advises you. Then after the meeting just use the fact finding to decide where you want to put your effort.