Tummy tuck with umbilical and diastisis repair 4 years ago. Is this indent normal or should/can I fix it? (photo)

If this indentation is a problem for you, you might have it filled with a fat transfer. This could be done in the office under local anesthesia. You could also try a series of Sculptra injections to help fill in that area as well.

after tummy tucks and at this point, the need to address it depends on how much it bothers you.  If it doesn't, don't worry about it.  If it keeps you from wearing a bikini, then consider addressing it with fat grafting as that is much more reliable than trying to make the other side indented too.

It’s hard to say from photos alone whether your issues are primarily skin or abdominal wall related... that notwithstanding, relatively thin individuals (especially those who didn’t have quite enough skin for a ‘full’ TT as evidenced by the small vertical scar above your pubic area) will need to consider an incision modification if they wish to revise their TT.  In your case (like most), this means that if the abdominal wall and skin issues are to be resolved, you will likely need to have a an extended vertical incision from your belly button to the horizontal incision. In my view, whether that is worth a flatter tummy and better contour to you is the crux of your decision at this point.Good luck