Nope, it's still not possible no matter which postage method was selected.
Wait till the first auction finishes and see if they pay, that solves the issue as you then pack and post the item.
If they do wait for the second auction to finish and then they ask to combine, you can explain that there is an issue combining postage and you are left with 2 choices.
They either pay for both postages if sent together, you can then make a partial refund for the excess postage paid, if you paid for the postage, eBay refund if this was a SD postage.
Or, you can cancel the items saying buyer requests to cancel , this will refund the buyer and your seller performance is not affected , then relist the items together, so you'll have one postage label, and one tracking number.
If the buyer paid for the original labels, they will be refunded for this.
You'd need to message the buyer to explain the actions taken above, and make it very, very clear in your messages that the items being delisted will be relisted for the buyer to buy on eBay again . Make it clear this is Not an off eBay sale, as eBay do read all messages going through their system.
@blackpoodleretro
