So my suggestion is : Please consider making an option to save our characters and then be able to join our friends by importing it to their campaign.
If DOS 2 was designed in the same way as DOS 1 - and I suspect it was - I do not believe that is possible to do.
Quests are spread out, and have multiple solutions. It's possible for Playthrough 1's characters to have done quests in a certain way, meanwhile Playthrough 2's characters have not done the quest at all, or have done it in a completely contradictory way.
Playthrough 1's characters are all level 5, Playthrough 2's characters are all level 9.
The way DOS 1 worked, it was completely, totally impossible to separate a character from the campaign which had happened so far.
Now, perhaps Larian has redesigned the systems so it is possible, but I think that's unlikely.