I don’t like my hairline. Can I fix it with another hair transplant? (Photos)

Yes, you can add more grafts.  What I would do is first determine if you liked the location of the hairline, if not I would put it where you wanted it to be. Then, I would certainly create a transition zone of single hair grafts (about 450 of them) so that the hairline looks like a no-hairline hairline. You should never be able to connect the dots on a hairline. Then I would fill it in where it is less dense.  I would imagine it might take another 1500 or so grafts to accomplish this. Pictures show your hairline on the left and a repaired hairline on the right, fixed as I described.