Is lipolysis of double chin a safe procedure and does it interfere with chin or jawline filler later on?

If you are referring to lipolysis of the submental area (neck under the chin) with a product like Kybella, this is considered a safe treatment. The risk of complications such as nerve injury are possible but very rare. The treatment will not interfere with fillers but may make liposuction and insertion of threads more difficult in the future due to fibrosis caused by the treatment. If you have significant amount of fat or you want more precise contouring, you may be better off just having a liposuction by an experienced surgeon. The results will be better and it's one and done rather than multiple treatments with down time. Lipolysis often requires 3-6 treatments for best results and the swelling can be significant with each treatment.