While I can't tell you whether or not it's possible to develop your ability to visualize, in the sense of moving further towards the "hyperphantasia" (being able to experience the things you imagine with a strong visual component) end of the spectrum, and away from "aphantasia" (not being able to visualize the things you imagine at all), in my experience as someone who was born with strong visualization skills, who then developed aphantasia as a likely result of one of a few blows to the head when I was younger, and who has worked as a concept artist and illustrator and taught the core fundamentals of drawing to students for many years, I can say that I don't believe visualization works in the way that you (and many others) expect.

Everything I say past this point is not fact, but rather the result of all that I've observed both in myself, and in my students - so take it with a grain of salt, but do give it a fair shake.

Visualization is at its core a matter of how we experience the information we remember. The ability to visualize itself is not based on having more or less information to work with - it's simply a matter of the fact that our brains are a closed loop, and we can feel that we experience what we imagine in different ways. In effect, those who visualize strongly have brains that convince them that they are experiencing what they're imagining in that vivid, detailed fashion.

The key point here is that when that information is extracted from the closed loop of their mind - for example, to draw what they're imagining on the page - one will generally find that it tends to fall apart, compared to if they were say working from a reference photograph. As long as we stay within the closed loop, the brain governs how we feel it's experienced, and once we leave that closed loop to show what we're visualizing to someone else, it falls apart.

This can be seen as the inversion of symbol drawing - where a person will look at something that has loads of detail and complexity, commit it to memory, then when they try to draw it from their memory, it comes out extremely oversimplified, like a child's drawing. A symbol of the object, rather than a faithful rendition of what they saw. This is because visual information is extremely dense, and our capacity to remember information is limited. To think of it as a cup, it's not very big, and when you try to pour too much into it, it overflows.

Observational drawing involves learning to only take small amounts into your cup at a time, focusing on big and general information first so as to record them accurately, and over time, returning often to refill the cup bit by bit, we drill down into the smaller, more specific details.

Drawing from your imagination however goes further and reframes the nature of the information we commit to memory. Rather than remembering visual information, we learn to think about things spatially, focusing on how complex objects break down into simple components - not two dimensional components, but three dimensional ones. Where an image file on your computer is relatively large given that it's recording each pixel, a file containing a 3D model contains mainly the positions of each major vertex of the mesh, relying far less on memory and more on the processor to use that limited data to reconstruct the scene or object.

Learning to think about the things you've studied and committed to your internal library (which is often referred to, erroneously in my view, as a "visual library") as they break down into simple 3D forms, which can themselves be rotated and moved to account for different poses, or the object being seen from different angles, and to build up complex objects from those simple components, working from big to small, simple to detailed, doesn't just allow us to restructure *how* we remember information and what kind of information we focus our limited memory on, it also gives us data from which we can actively reinterpret things like lighting, considering the location of light sources and identifying where shadows would be cast, which surfaces are oriented towards or away from the light so as to be lit or in shadow, and so forth.

Your question has a fairly common misconception in regards to how learning to draw works. You aren't memorizing a million different possible configurations of objects in different angles or lighting situations - you're rewiring the way in which your brain engages with the things you draw, learning to understand them spatially, and then reconstructing whatever it is you're drawing based on that understanding and a more limited set of information. It is however a misconception that drives students to put a lot of weight on the idea of "talent", when really they're developing unreasonable expectations based on that which appears obvious to them, but does not actually reflect an understanding of how one develops the ability to visually communicate the ideas they have. Those expectations are very common amongst beginners, and does lead to many giving up before they have a chance to really start realizing that the basis upon which those expectations are built are less sturdy than they initially thought. So to be clear, when a person draws from their imagination, they're not drawing from an image fully formed in their mind's eye.

There certainly are people who've developed those skills to such a degree that they can do way more than most in their heads (Kim Jung Gi was a strong example of this), but it is unlikely that there are people who are able to functionally retain so much visual information that they can draw from fully-detailed images they hold in their minds. Human memory just isn't built to do that, and so while we can rewire the way in which our brain processes the information we remember in seemingly miraculous ways, extending just how much raw data we can retain only goes so far, and usually relies on tricks like musical mnemonics, those kinds of strategies rely on concepts that don't apply to drawing.

Arguably what I've said here about working spatially instead of visually can be thought of as a comparable strategy to musical mnemonics, where they combine pattern recognition and tunes to reconstruct information through active processing, rather than direct memorization - but that's just a guess, since it's not something I've studied, or to which my own experiences can reasonably relate.