When having a duo treatment of PDO threads and filler(s), which do you recommend doing first? Together or separate appts?

Best results achieved by combining threads with bio stimulating fillers . I prefer to use threads first ,  after tissue is lifted you need to use less amount of fillers . Procedure can be done same day , or threads can be placed first and fillers can be added 2-3 weeks later .

I agree that PDO threads should be done first.  The amount of filler requirement may be reduced once the lift is achieved and you will already be anesthetized there in the office and ready for filler.  Alternatively, the swelling from the PDO threads will be resolved in 2-3 weeks and the injector could better judge any volume deficits then so if you are not in a rush for a particular event as you suggest, you can do it stepwise if you don't mind and additional visit and possible swelling and bruising a second time.