There is a few approaches to achieve your goal:

1. Helper. If it's some complicated logic you can move it into shared helper class (something like 'shared/***.helper.ts)
2. Inheritance. You can create parent component with all common logic and inherit it with 'extends' functionality. (You can read more about it here: https://www.bitovi.com/blog/4-reasons-to-fall-in-love-with-angular-component-inheritance) I personally don't think that this is the best practice for frontend, but in some particular cases it might be reasonable.
3. Service. You said that you don't want to use service for that, but it's actually a valid architectural solution to use services not only for API interactions.
4. Code duplication. If we are talking about some small functions which describe simple elements behaviour - it's okay to have small pieces of code duplication in different components.