I’ve already raised this issue, but there is currently no good solution for bulk adding/removing media to products and variants since those fields were removed from productUpdate. Also mediaId on productVariantUpdate only works when creating the variant.
We need this ability back on those mutations (similar to how images worked) so we can use them in a bulk operation. Otherwise it looks like we can use the productSet mutation, but the issue is we have to include all the variants and options, which isn’t necessary if we just want to edit the media. This makes the input file much larger than necessary, and will exceed the 20mb limit for a bulk operation a lot sooner.