My range is pretty much zero. A buddy of mine is like a 2 out of 5. I didn't realize that folks actually meant imagining until about 8 years ago. I thought they were just declaring a mental space, kind of like a chalkboard.
I have a lot of concepts of what things are - I believe it helps me appear smarter than I am. While a normal human has a ton of image processing to do, I don't.
Songs don't get stuck in my head. I don't remember physical pain. I don't know what things taste like - what is garlic? What is salty? I was able to quit smoking pretty much instantly - I don't remember the habit (there was a short physical withdrawal, but that was it). I give off a stoic vibe, probably at least in part because I can't carry mental trauma around.
I don't know what my partner of 13 years looks like, beyond a string of concepts. What they sound like. I can't be hungry for a certain thing, I don't know if my vodka red sauce is different than the last one I made. My "vivid" dreams need to be written down within a minute or two of waking , or it's gone. Concepts only - but it feels like imagining. For me to paint a realistic surf hitting a shore, I need to have a picture of it. While I paint, so I can reference it the whole time.
I love Blender. I can 3D model things finally, without tons of pieces of paper to fake it. I can include reference pictures while I design.
For you normals at 5 of 5, that's a lie. There are folks who can voluntarily hallucinate better than you. Song stuck in their head? They'll start adding new instruments, or remove instrument lines. There's the guy who can imagine listen to FOUR symphonies at one time (Bob Milne).
I would prefer to be normal though. It's tiring, trying to problem solve, knowing that everyone else has access to a common tool. There are trivial arguments with people, because you appear to be willfully dense. I hurt people, not recognizing them outside of the context where I know them. (My neighbor friend from across the street brought cookies, and I stood at the door treating him like a stranger.)
I wonder sometimes even sharing - maybe a future work lead will evaporate, because they don't think I would be able to do a task without being able to voluntarily hallucinate.