Swipe an item to the left and tap the pencil icon:

Please note that as a result the initial version of the product name will stay intact in the dictionary and the new item with the new name will be added to it. This feature is convenient to use when you need to create several similar products with a slight difference in the names. For example, you can edit "Cookies" to add brands to the product name instead of creating new products manually.

By the way, if during the editing you just delete the initial text and do not add any of your own, after you save the changes the previous version of the product name will be saved.