Meritocratic Regency & Changing to Primogeniture?

[Aetini]

I'm playing in Korea as a noble family and the kingdom changed to Meritocratic Regency at some point recently, which led to a family member being the Regent Ruler.. Currently I'm at the cusp of a character death and I can play as the Regent Ruler if I wish (or a powerful king-level Intendant, if that's a better approach still).

If I understand this right, I somehow (I do not know how to do this best) need to take the Ceremonial Monarch title & also hold the active Regent Ruler title at the same time.

Assuming I am already the Regent Ruler:
Anyone got a good explanation/tips on how to go about taking the Ceremonial Monarch position and changing the kingdom from a Meritocratic Regency to Primogeniture again?

Many thanks.

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PSA: I think I figured it out, sort of. Basically I just obtained the Regent Ruler title and then did Depose Ruler on the Ceremonial Ruler. That made him abdicate and gave me the title. The plot itself was rated as very difficult so keep that in mind. In my case, though, I still easily did it due to have a good high intrigue character and the Ceremonial Ruler was a kid.
I'm unsure if him being a kid is what allowed me to do it or not.