thank you ...
Don't thank me too soon.
If you have a gas canister with 100% butane in it, that contains 220g of butane under pressure. And you decant that into one of equal volume, then you will get 110g in each canister. Cooling the bottom cyclinder do say -15°C (totally doable with a domestic freezer), will increase this yield somewhat, but you're still going to get approximately half the gas in one, and half in the other. Either way, you're not going to empty the top cylinder into the bottom one, you can't push a fluid up hill (unless you have a Haskell pump). If you want to increase yield, you'll want to cool the bottom cylinder continually while it's filling (pressurisation will make it hotter). You can do this with an ice bath with salt added. But you're still going to get that pesky issue with pushing a fluid up hill...
This is before we get onto the issues with the fact that most of the dirt cheap bistro gas canisters are purely butane, which means that they don't work below about 10°C (plus or minus), unless you have a remote canister stove.
In short: Nice idea, but the yield isn't quite as good as you would like.
Note: assumptions are made on volumns and pressures, and gas laws. YMMV