For endoscopies if sedation is used its usually midazolam. Could that be what you mean by ‘twighliight’? This does not cause an unconscious state and a patient is fully able to move around at will - and they often do, a lot.
With most surgery it’s pretty imperative that your body is motionless as a slipped scalpel could be highly dangerous. With general anaesthesia a paralysing agent is usually given that prevents movement, so I can’t see how ‘twighlight’ sedation would be a viable option without risk.