The one thing that IMO would make a useful additional feature (might be already requested?)
In the Tone Curve controls ~ a picker to select a point on the image that would place a fix on the curve line. This function ideally needs to allow for picking multiple points on the image so that when adjusting the curve, specific slight changes can be made to the Tone Curve based on those chosen points in the image.
TIA
PS for more control ~ right clicking on a point on the curve allows its deletion/reset, if required rather than resetting the whole curve