Sim baby greyed out
I played another household, and when I returned to another and realized that my pregnant Sim already gave birth. She was supposed to have twins. So when I edit my Sim, the baby is greyed out (although playable). I didn't get to choose their traits either. I left the game to manage world without saving but nothing changed. I'm not sure what to do about this.
Babies cannot be edited in CAS. That's why the portrait is greyed out. You have to wait until they age up to toddler to edit them - change name, hair, clothes, etc. When a baby ages up, you get a pop up to give them their toddler trait without going to CAS.
If you have Nifty Knitting, you can knit a baby onesie and put it on the baby by clicking on the bassinet. Otherwise, you don't have any options to dress a baby.
Hope this helps.