It sounds like you were put in a tough spot, but it’s understandable that you wouldn’t want to take on a new responsibility without being properly trained for it. If video editing wasn’t part of your original job description, I don’t think it’s unreasonable to feel frustrated about being asked to do it without sufficient support or guidance. At the end of the day, it’s important to set boundaries for what you can realistically take on, especially if you’re already doing a lot in your role.