How to enlarge the size of the preview images on the Backoffice products page?

[mpscholz]

Hi,

I need to enlarge the size of all the preview images on the table of products in the Shopify Backoffice (https://admin.shopify.com/store/***/products), since they are way to small  for me to work with them efficiently.
However, I did not find a way to achieve this yet and no documentation regarding that.

Note that I do not want to change the size of the preview images for the end user in my Shop itself (by editing its theme or the likes) , just the ones in the admin products page.

Thanks, 
  MP