I'm a staff security engineer and my team was rescoped to Software Engineering. I'm nervous that I won't be able to keep my high performance as a software engineer at similar level because its not what I've been trained in. I've expressed this to my manager whom is also a new manager himself. I'm not sure how to handle this, do i just quiet quit and spend my time training until I'm let go or still contribute in hopes that I will make it through next round of interviews?
A domain switch will definitely hit your productivity and performance in the short term. However, I do think general software engineering has a big benefit over security engineering in the market: Flexibility
All that being said, the biggest factor here is you and your passion. Do you genuinely love security engineering? Then I think you should stick with it. Are you maybe getting tired of it and are open to trying new things? Maybe give SWE a shot. As a Staff Engineer, you have options. Junior engineers on the other hand need to pragmatically stick with what they already know just to survive.
Here's a good related thread: "How do I know when it's time to leave a team/company?"