Turn off multiple slot smelting

How do we turn off multiple slot smelting off? We just want 2x of vanilla and only one slot smelting at a time.

No one?

(Duplicate post)

ITSB

No one?

1+ for this the smelting speeds are already faster. this should be a option as vanilla is now only one slot at a time.

"Smelt all slots at once = False"