only update variations – import

My supplier sent me new 2021 variations

my aim is to import ONLY the variation option without touching the current parent product

In step 1, do I choose existing or new?

In step 3 how do I add only this specific NEW variation from an uploaded file?

Key thing is to link it TO PARENT, and it should have its own unique key so I could change this specific variation in future. (e,g stock)