A COD parcel is money somebody still has to collect. A prepaid parcel is already paid for. They go out of the same door to the same rider, and they are the two things you least want interleaved in one unsorted stack.
Tick Payment (Prepaid/COD) in the Sort by list. Part of the free crop — no coins.
Prepaid is settled — hand it over and move on. COD is not: the amount still has to be collected at the doorstep, the buyer can still refuse it there, and it is the half of the batch worth slowing down for. Handled as one stack, that check either happens on every parcel or on none. Handled as two, the COD run gets the attention and the prepaid run gets out of the way.
Nothing is entered by hand and nothing is looked up. A Meesho label prints the word Prepaid on the page, or else tells the rider to collect an amount — that wording is what marks it COD. Flipkart puts the mode next to the order ID as a single token, which is why a Flipkart batch can separate four ways rather than two.
Payment (Prepaid/COD) is an ordinary key in the Sort by list, not a mode that takes the sort over. Ticking it adds a numbered position to the chain you already have, so Courier Partners first and Payment second gives you each partner's pile already halved into COD and prepaid. Flipkart has no courier sort — its list is Sold by, SKU and payment — so the pairing that earns its keep there is Sold by, then payment.