Division?! Small room / steep slope / radiator

I would do it similarly. Without a loft bed – as Climbee already said, it looks great, but in practice it can just be annoying. Vacuuming, making the beds, etc. We built three lofts for the children; we had more space than you in height, the lofts were also 2x3m large, yet the children only slept downstairs after a few months. Upstairs was then only Lego/drums, etc. Fears cannot disappear through nagging and better parenting. Usually, time helps with that, and enforcing things by the parents doesn’t benefit anyone. My sketch is also not to scale – it’s only meant as an idea.

Then I would plan the bed so that the feet go into the lower part. At the head, you could possibly use a shelf as a room divider and "protection," creating a cozy nest but not having your head in the "dangerous" niche.

When I was 6 years old, I was afraid to go into the (bright and cozy) basement, and every time I went to the bathroom, I looked to see if there was a snake inside that could bite me in the butt. So fears are irrational. If possible, I would also take that into consideration.

I would do it somewhat like that. Without a loft bed

Exactly like that How is a loft bed supposed to fit here as you suggest? It doesn't work. Especially since, in theory, the loft bed would be very close to the slope, which is not desired.

and every time I went to the bathroom, I checked if there was a snake in there that could bite me in the butt. So fears are irrational. If possible, I would also take that into consideration.

I always thought that someone “lived” under my bed. That’s why I jumped into bed. I always slept very well and not anywhere else.
I always thought you had to overcome irrational fears?

Exactly, the feet towards the [Drempel] and maybe even a nice shelf at the head of the bed to shield the bed a bit from the door. Or a nice curtain?

how is a loft bed supposed to fit here, as you suggest.

I would not have matched the posted plan and the photo. I retract the loft bed.