When creating a configurable product does anyone know of a way to add a custom product attributes to the variations grid so you don't have to then go into to each simple product and enter it in seperately. Screenshot of the area I mean below.
You won't be able to change those values in the same way you can customize the general grids. I guess (I'm not sure becasue I didn't tried) this is build using ui_components.
You will find the definition at vendor/magento/module-configurable-product/view/adminhtml/ui_component/configurable_associated_product_listing.xml (again, I didn't tried but maybe you can start looking at that file).