I suppose you can set up trades in the Alola games for them prior to moving them up to Home. Of course if you made the mistake of moving your offer into Home already, tough luck and too bad, it's now worthless and stuck. That said, trading events is generally just a mess, always has been. Most events that people are willing to part with are hacked, even on serebii forums. I know I'd never part with any of my events that I got legitimately when you can't ever know you're getting something legit in return. That said, this iteration with Home is literally the worst since internet trading came to pokémon. People having to have living dexes with unusable pokémon stuck in Home, to receive a Magearna form that is also stuck in Home and literally unusable, just there taking up storage space in Home. It's just dumb, like why? What's the point in moving pokémon like Magearna and Deoxys up to Home, only for them to get completely stuck? To get a new Magearna form that's also worthless because it literally can't be transferred to any game?