Are there any current, plausible approaches to the development of antigravity technologies?

We hear of gravitons -- hypothetical subatomic particles responsible for the mechanisms of gravity. We hear of gravity waves. We even hear of clear evidence for the existence and detection of gravity waves. So, currently, most physicists believe in the existence of gravitons, and virtually all physicists believe in the existence of gravity waves. So, in principle, it would seem that it should be possible to manipulate gravity in ways similar to the way elements of the electromagnetic spectrum are manipulated. It should be possible to turn gravity on and off, to increase and decrease its intensity, to reverse its force. Are there any current approaches to these problems that seem practical and likely to yield meaningful technologies in the not too distant future? If not, why not?