Tap the ≡ icon on any deck row. A panel slides open showing every card inside, in order. Use:
· ▲ / ▼ — reorder a card up or down
· × — remove a card from the deck
· + Add cards from search — jumps to search with this deck pre-selected, so anything you tap +Add on lands here.
Removing a card from a deck doesn't affect it anywhere else — it's still in search, still in your other decks, still on your trade dashboard if you hold it.