I agree with the comments from several of my colleagues on this question. 3 months is a fairly good amount of time to have seen some difference in these dents. Continued massage is a good idea. fat transfer is a reasonablke remedy for this solution.
ConsideringThatBoth of theseHave not yet workedIt may be time to considerA second opinion
Depressions on the forehead after brow lift can occur and are usually only temporary. The dent may be caused by early fixation of the soft tissues down to the bone at that spot or excessive swelling around the spot. Digital massage is always helpful in managing healing soft tissues and should be tried. It may be getting to long since your surgery for this to help much. A filler of some sort may be necessary. I usually use Radiesse because it's a thicker firmer filler and lifts the soft tissue better than fat. After several more months, a local undermining may be required in order for the filler to be successful.
Maybe your surgeon does not use the Coleman fat grafting techniques with rigotomies??? This should be an easy fix with fat...
Dents in forehead after forehead lift are not common. If they are in the skin itself a filler like Voluma or Juvederm can be used.
Indentation are not uncommon after a forehead lift. Whether or not this will get better over time depends upon the type of forehead lift that was performed.