Currently, at many places in the administration, there is the option to use an auto-completer to add values to a field one at a time. An example for this would be "add products to a 'product is one of...' field in the rule builder or the selection of products assigned to a category.

It would be helpful to paste a list of identifiers (e.g. product numbers) into these fields and get them assigned in one go. Specifically with large lists, that would save a lot of "clickwork" in the administration. Some simple reporting (failures / successes) in a message window would be helpful.