Just to rehash this question (although I believe
Unterwegs has already answered it):
I have an itinerary LHR-ZRH-YUL, all on LX. I have about 5h in ZRH. My luggage allowance is ample.
Can I check in 1 bag LHR-YUL and then add a second checked bag (stuffed with chocolates, of course!

) for ZRH-YUL?