Mission Planner is made for ArduPilot. Unfortunately, the mission upload protocol (using of mavlink) is slightly different between PX4 and ArduPilot, and in this case that’s preventing the successful transfer, unfortunately.
1st I don’t think that’s supported. You have to add that to QGC yourself, convince someone to help you do it, or find a consultant too add it for you.
2nd You could try to add several surveys after each other as you can have several per mission. Or just create polygon in a way how you need it. I’m not sure if polygons are possible for surveys, I’d have to try it out.