How can I add a variant choice to my product on my e-commerce site?

[Keyla22]

Good morning everyone, I'm new to shopify and I would like to add the option to choose in addition to the size variant, an option where you can add if you want it to come with an additional plugin of type a, b or without it to my product view and that depending on the option chosen by the client the price varies. I have thought about putting labels on the products that have that additional option because I don't want it to be for everyone, but I still haven't found enough documentation to be able to validate with the labels. I would be very grateful if someone knows or has done something similar because I couldn't solve it so far. Very grateful in advance.

Kind regards to all