Import related skus for configurable products

Shop-Version: Magento 2.4.3

I want to import related skus for configurable products.

The csv file has the following heading: sku,related_skus

This is working for simple products but when the sku is a configurable product, the import check shows an error that the product type is not supported.

Do i have to use additional columns for this or is it simply not possible with the standard Magento 2 import function?

Thanks