With all my sincerity and the best of intentions towards everyone:
We are already ending 2023, with +100 chapters of the sequel (from what I see in the forum) and I suppose with the story already settled. I think the best decision for your experience and enjoyment regarding King and Diane's children is to lower your expectations in certain aspects. Not even the author himself is going to develop such depth in 7 creatures. Nor is he in any hurry to reach the Fairy King's Forest's arc in the sequel.
Since the prequel manga ended, in all these years there has only been progress in knowing the number of children and the revelation of the youngest daughter. You can now get the idea of what the rhythm will be like until we meet the 6 remaining children.
Whether they are powerful or not; or the type of role that any of them would have in the sequel is, at this point, something that doesn't make much sense to take into account. Everything is already settled in the sequel, so their future appearance will not be as many are thinking or want to believe.
So as advice: Let's enjoy the revelations of their designs and/or names, let's theorize about their magical powers, the type of relationships they have with their parents, cousins, friends, etc.; as we have new canonical information that is revealed to us by Nakaba in interviews or projects other than the sequel.
Now we have
7DS:Origin as a project where we can see more about their youngest daughter, and possibly as the story progresses, we could learn more about her siblings or her life with her parents in the last 13 years after the end of the Holy War. The best thing for anyone who is a King/Diane fan (or at least for anyone interested in their family), is to focus solely on 7DS:Origin and enjoy its original story supervised by Nakaba himself (the events as such are obviously not canon , but Tioreh is, as well as her magical powers and her past linked to the main story).
From my part, I have no problem continuing to share any new information about Tioreh or her siblings in this thread, as well as discussing about the news with you guys (you already know that I love to analyze or theorize about this hehe

) We could also use this same thread whenever we want to talk about Tioreh's actions in Origin.
(I hope I have not offended or bothered anyone with my advise, I do so out of good will to avoid disappointments).