I do not have specific authors to point you toward, but I have a direction for you to conduct your search.
What you are looking for is the fusion of the idealist "mind-at-large" of the perennial philosophy with a version of the Epicurean/Aesthete ethic.
Mind at Large in Perennial Philosophy generates this universe, and small self-deluded minds like ours.
The Aesthete ethic takes a variant of the pursuit of Beauty from Virtue ethics, and the Epicurean model of the point of life being "experience" rather than the "agency" of virtue ethic, and raises VARIATION in experience to the highest value.
I have encountered in life, New Age thinkers who hod by the Aesthete ethic, and embrace living as many experiences as possible, from ecstasy to despair to extreme cruelty. They operate off the theory that our purpose in being reborn is to experience everything that is possible to experience, so set out to do as much as possible of that task in this life.
Extending the Aesthete ethic to Mind at Large addresses the Problem of Evil, plus an explanation for why our universe and we exist. MAL in that case would create evil, despair, etc. on purpose -- having toys (us) experience all of the above would then be MAL's GOAL for this universe.
The coupling of this view of MAL with Everett is interesting, and a good theoretical fit. Many advocates of Everett want to preserve determinism against the indeterminist Copenhagen model of QM. However, what Einstein showed is that determinist and indeterminist "interpretations" are actually DIFFERENT theories, with testably different outcomes. All of Einstein's efforts to develop an actual determinist fit to QM data, failed test cases against Copenhagen. Everett leaves our universe indeterminist. We cannot predict what will happen to us. That is why Everett gives the same predictions as Copenhagen does. Everett instead tries to put determinism in the collection of the universe -- EVERYHING WILL HAPPEN, and the collection of the universe in theory knows this.
So -- look for Aesthete idealist amoral thinkers who embrace Mind at Large, and you will probably find other advocates for this idea.
Note that I don't think these ideas actually mesh well with science. Take physics. Everett, for instance, generates new universes by decorrelation. There is no possible communication between decorrelated universes. Postulate a MAL that crosses between universes, and then one cannot have "neutral monism" because the mental correlates, but the physical does not. Your author was advocating for neutral monism, but what this actually leads to is pure idealism -- the MAL is the only real thing, and the APPERANCE of decorrelation of the physics is what is happening physically, while "reality" is correlation. Physics as a toy/delusion is idealism, not neutral monism.
Also take consciousness. MAL exists without physics, and created physics, so the whole neuro-science assumption of a physicalist source of consciousness is -- yet another delusion. Consciousness can be put into anything by MAL. Photons, your toenail, etc. And to complete the "every possible experience" objective, every possible "you" and every possible self of a toenail, experiencing infinite DIFFERENT thoughts would be sub-variants of the MWI of Everett.
Also take agency. Everett, among other things, removes all agency from us. Everything happens, so what will, is irrelevant to any outcome. We happen to be experiencing the delusion of willing, but the MAL would be interested in a full spectrum of experiences, which would include consciousnesses that experience the randomness of outcomes too, as well as perfect frustration of will, where we NEVER get what we will, etc. Our high correlation/experience of willing being consistent across millennia, is actually very difficult to explain per Everett or this Aesthete MAL, and is fairly strong evidence this is NOT how our universe is constructed.
There are, of course, massive ethical objections to this worldview. Numerous novels postulate amoral Aesthete motivations to their villains. And one of the major moral objections to Utilitarianism as a moral perspective is that experience is so SHALLOW of a motive for ones life. This is the basis for pursuit of virtue ethic, where agency, and who we are and what we make of ourselves, are morally important. This is the difference between being a do-er vs being an experiencer as a life goal.
So -- I pointed you to a category of thinkers where you will probably find other advocates -- among the Idealist, Aesthete, New Age thinkers. And I pointed out problems for this worldview, both ontologically (it is not neutral monism), physically (Everett's physics prohibits the cross knowledge of a MAL, unless physics isn't actual reality), neuroscientifically (neuroscience would be irrelevant), and morally.
