I've had to add some custom fields to a group of products, which can be done by:
- adding each custom field to each product in the group
- adding each custom field to the first product, then deleting/recreating the other products through Duplicate Product, and adjusting prices & other product details...
It would be so time-saving to be able to copy custom fields between products, or;
set custom fields at the product group level inherited by the products in the group.