I have to write a rebuttal for a machine learning conference in which I included a lot of new references (to prove broad interest). The rebuttal has a page limit of one, and my reference list is too long for that. Is it ok to cite the paper by only using the DOI in the rebuttal, if I cite the works in full in the actual submission in the final version?
Yes, that's fine. Contrary to Wolfgang's answer, the DOI is the easiest way for a reviewer to find your reference. They can simply use the DOI resolver. The advantage of DOIs is that they always find the document in one step. Traditional citations do not necessarily do that.
Make it easy for your reviewers to get what you are saying. Just a DOI is really hard for a reviewer because they have to walk to the computer, look up the DOI, and all that.
If you don't want to provide the full reference, just say "see Schneider et al., cited in the paper". That way, there is an easy place to go to to find the full title and reference.