Clear all attributes that aren’t variations

Hello, quick question about the plugin. Can I bulk clear all the attributes in registered in products that aren’t set as variations. And if yes, can I prevent on specific attribute to stay event though it’s not set as a variation.
I have sizes attributes (let’s say S, M, L, XL, XXL) and brands (adidas, nike, blabla).
I want to be able to clear all sizes attributes from products that aren’t set as variation (example I’ve set S, L but no M and XXL even though they are set as attributs in those products BUT NOT as variation). And doing so, I want to leave all the pa_brands attributes in the product even though they are not set as variations.

Thank you for your time