What options do I have for revision lipo on my chin after a fat graft followed by initial lipo that left scar tissue?

I suggest you get a proper assessment.  That means providing detailed and accurate information to a competent provider who can determine if another procedure may or may not be appropriate for you.  The majority of people who seek chin liposuction especially young people who are not overweight have a mandible that is small or lacks projection rather than having too much fat in that area.  You could try reposting with proper pictures but that will not be as accurate as having in person consultations. At this point you cannot afford anything but competent and accurate recommendations so put in the work and start having in person consultations with local board-certified plastic surgeons.  Your post does not really give us anything other than the need to explain the above.  Best, Mats Hagstrom MD