Very late to this but since I had the same question, the function you want for inverse lerp is FMath::GetRangePct.
FMath::GetMappedRangeValue is effectively the result of an inverse lerp on one range, and a lerp into another range. You can use it by giving it a 0-1 range but that’s a waste since GetRangePctis what it uses internally for the first step.