Here's a classic story. You do well at your job & you get promoted to senior engineer.
But you don't FEEL like a senior engineer. Just because you got a promotion doesn't make you feel like you're a better developer.
You start to question, "Did they make a mistake promoting me?" & "When will they figure out I'm a fraud making it all up as I go?"
There's no magic way to convince yourself that you're senior. There's no trick to beat imposter syndrome.
Here's one helpful idea for me:
We're all just making it up as we go. Senior engineers just have more experience improvising.
Once you realize that everyone is improvising just like you, it shifts your perspective.