Add drastic to family library on Google Account

[MDLuffy]

Hello. I want to add drastic to my family library because I've bought it before the family library feature. How can I do that?

[xperia64]

I will ask Exophase to see if the option to allow previous purchases into the family library still exists.

This mentions how to do it, but the answer it references no longer exists, and I couldn't find the option on my own personal Google Play console, possibly because I've already enabled it for my apps.
https://www.androidpolice.com/2016/05/1 ... -july-2nd/