Advice needed

Hey everyone, I've been working with this MNC for over three years now, primarily working on one project since the beginning. Lately, I've been feeling like my growth has plateaued, and the work has become quite monotonous. My manager has mentioned that exciting new development tasks would be coming my way soon, but unfortunately, these opportunities haven’t materialized for over a year now. I'm at a crossroads and unsure of the best course of action. Should I consider resigning to actively pursue new opportunities, because preparing for interviews while working and managing a 90-day notice period might be challenging? Or should I continue on with the current project while simultaneously exploring new job options? I'd really appreciate your insights and any advice on how to navigate this situation. Thank you!