Not sure how many retainers you're using, but it makes life a lot easier if you just organize things a bit. I have 1 retainer for materials and 1 for armor/ weapons. My materials retainer gets pretty full sometimes, especially after leveling a new craft (only 2 more!) so I've thought about adding another. If you're using more, just do metal/ stone/ wood on one, cloth/ reagents/ skins/ food on another or some other combination you find useful. It helps to name them appropriately too. My armor/ weapons retainer is named Armoury, for example.