Issue opening LootItemSet_SupplyDrop_*

If I try to open any of these blueprints, the ark dev kit freezes and sits there, doing nothing… It’s now been near 12 minutes, and my PC is NOT a low performance unit. Is this normal?

Yes and no.
The ADK is pretty notorious for randomly showing horrible performance. LootSets have quite a few references, too: all the items and their respective crates, and by relation, anything referencing those items/crates.