You're right, the Wardrobe account is tied to your UUID, so you can only have one account per avi.
The standard way is to tag the items appropriately, so you can distinguish between different types of items. You could then create tag sets for these items, with which you could create a "view" that will only show the respective items when a tag set is activated.
Alternatively, you could purchase another Wardrobe on an alt and use that, e.g., for building/decorating items, for which you don't necessarily need the wearing functionality (the communication with the HUD is also tied to the UUID).
Or feel free to get in touch if you have already purchased a second copy of Wardrobe; I can transfer that to a second account on a fake UUID if you don't have an alt.