I know I've seen it somewhere, but I'm absolutely lost where. I'm looking for a mod that sorts the sim portraits by age instead of names.
For example, let's say we have Jane, who is 6 days to elder, Emily, 18 days to elder, and Ryan, who is 1 day to elder.
How the game is now, the portraits would look like this in order:
Emily - 18 days to elder
Jane - 6 days to elder
Ryan - 1 day to elder

With the mod I saw, the portraits would be
Ryan - 1 day to elder
Jane - 6 days to elder
Emily - 18 days to elder

As now they're sorted by age. Would anyone know what this mod is and where I could download it?

I'm confused. In my game the portraits are sorted by age, by name only when they are the same age, and I don't remember ever downloading a mod for that. Are you sure, you don't have a mod that changed it already to the wrong thing?

That may be so: I have a mod that assigns a random # of days for adult sims.
I guess the game sorts by days lived, nor days left until the next life state. In that way, yup, they're all the same age

It sounds like your mod that assigns a random number of days for adult Sims is also affecting the portrait positions.

In a default game without mods that affect things like that, it is based on the days until the next life state. Only Sims that have the same number of days left until the next state are sorted by name.

They were all made in CAS and would all be the same age in a vanilla game, that's why I'm assuming that it's sorted by how many days a sim has lived, since in vanilla they would all have the same days left until next life state