My drain was taken out 4 days ago and I’m leaking a yellowish mucus substance. Is this normal? (Photos)

Thank you for your question.
It appears that you had a Tummy Tuck procedure. It is difficult to give any advise without a picture of the wounds. Thick discharge at this time, is not normal. You should see a surgeon preferably a Board Certified Plastic Surgeon who can evaluate you and guide you. All The Best !

In general, thick fluid coming out this far after surgery is not normal. Perhaps some clear fluid for a day or so.  You need to be evaluated by a surgeon with expertise in tummy tuck care.