How do I indicate mythic+ cache loot in the simulator?

How do I indicate that an item I want to equip in the simulator is a high level mythic+ cache piece? The problemI have is this: I have a corrupted ilvl 470 belt that I got out of the mythic+ cache today that I want to test without the corruption. The closest I can get is choosing the same belt at mythic 15 which puts it at ilvl 465, and I see no way to simply modify an already equipped item.

I’ll add the option to titanforge (modify the ilvl) of items on the UI, even though they don’t drop like that for the most part. Then you’ll be able to try any variant.