External (custom) component - how to include other components?

Hey,
I’m working on a custom (external) component for my rolling gate controller. For now, it’s implemented using the Cover base class. However, I’d also like to use further controls as I can program the gate controller via UART as well. So I’d like to include a few custom buttons and drop-down (select) components.
The problem is, I don’t know how and can’t find any guidance. Could you please help?

It may be easier if you can see how it’s working for now:

Question is: in the cg yaml, how do I include buttons, selects etc with predefined values that show up as entities? (I think I know how I could interact with them in the actual C++ code, that’s not the difficutly for now)
Thanks a lot!

Just add any component you like, from the massive list here. esphome.io