...there is no way to store/unlock equipment appearances permanently. What that means is that you need both the base item and the Transmog item present in your Inventory, so when you sell your junk Gear, as you periodically do, you'll also lose the ability to Transmog since all your templates will be gone.
This obviously leads to some serious logistics problems because no one in their right mind will carry around, or store in a chest, a single copy of every possible Gear piece to have it available as a template for the Transmog system.
As it stands it's just far more practical to use the Visual Adjustments 2 mod instead, which is quite unfortunate. Hopefully Owlcat will add some sort system to permanently store the appearances of the Equipment pieces you've already picked up or used.
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