If you want to have a separate add to cart button for each product variation, then this module is for you. Beside showing buttons for each variation, there are additional settings, like option to display or not price, currency and quantity. You can also choose which product attributes to show in your add to cart form.
To use this module you must have Drupal Commerce 2.x installed. This module was created for one of our projects, and it is still in a development phase, just like Drupal Commerce 2.x, so if you find bugs or if you want to suggest a feature please open an issue.