If I were to frequently work on sensitive data on a LUKS partition and wanted to be able to quickly destroy the keys to it, I figure it would make sense to—
encrypt that partition with a key file,
place the only copy of that key file on some sort of removable medium,
come up with a plan for destroying that removable medium quickly,
carry the removable medium (and equipment to destroy it) everywhere.
That way, if The Final Reckoning arrives, I can immediately destroy the removable medium, making the partition's data inaccessible.
The difficulty lies in choosing a medium which is both easy to use and easy to destroy.
USB sticks are convenient to use: just configure the boot partition to read the keyfile from there. However, they are difficult to destroy quickly and reliably, necessitating destructive tools that are difficult to carry safely, and illegal to take on planes.
QR-codes printed on paper are inconvenient to use: I don't know of any LUKS implementation that allows key input by QR-scan. However, they can be destroyed without equipment, by just eating the paper.
Memorising the key is both inconvenient to use (takes a while to rehearse, then have to type it in every time) and difficult to destroy (voluntary forgetting is difficult, though it is plausibly deniable).
How could I get both?