In Mass Effect 3 I've missed the meeting in hospital with Thane and now the Salarian Councillor is dead. What should I change with the Gibbed Save Editor to save him? I didn't romance him.
There is no way for you to simply "change his fate" with the save editor I believe. It does not matter anyway, the only thing he would do if he was alive was:
No matter if you romanced him or not, the only way to change his fate is through the ThaneMOD.