Recently, I visited Muiden. UNESCO states that "Muiden Fortress" is part of the World Heritage Site: Defense Line of Amsterdam. But I was wondering, which buildings in Muiden are part of this WHS?

as far as I can gather it certainly includes:

the barracks (kazerne)
Muizenfort
western battery (westbatterij)

But what about the great sea-sluice (groote zeesluis), the pepperpot (peperbus), and or any others?

The whole site in my opinion badly needs some detailed maps explaining which is part of the site and not. Cause what about small additions to the fortresses and polders, canals, dikes etc?

I visited Muiden a few years ago.
I am pretty sure it was only the West Battery by the tiny beach and Muizenfort that were inscribed.This page has a full list of the inscribed sites. It doesn't mention the Kaerne though, I think I missed that one myself when I was there.
If you have Google Earth, you can get the locations on there by clicking on the 'Show Multiple Locations' tab on the inscription. It helps to give a good idea of the ring the forst form around Amsterdam.

I visited Muiden a few years ago.
I am pretty sure it was only the West Battery by the tiny beach and Muizenfort that were inscribed.This page has a full list of the inscribed sites. It doesn't mention the Kaerne though, I think I missed that one myself when I was there.
If you have Google Earth, you can get the locations on there by clicking on the 'Show Multiple Locations' tab on the inscription. It helps to give a good idea of the ring the forst form around Amsterdam.

The Kazerne is in front of the Muizenfort, though it looks like a grass covered hill surrounded by a fence from behind. Only the front facade is clearly visible. According to information I read there, it was built in the same year as the muizenfort, and I found the style to be very similar.

I know of the subdivisions on the world heritage site, but I find it weird that a WHsite that is all about the flooding of the surrounding areas does not seem to include smaller building as sluices or dikes. Surely they play a part in the process, and if so, shouldn't they be part of the WHS? A recent evaluation file stated appropriate maps and borders are requested.

Also, this site, which seems pretty official to me states that muizenfort is "a part of" muiden fortress. In dutch Muiden fortress is called Vesting Muiden. Which I interpret as fortress town muiden, meaning multiple parts.

The west battery is included seperatly on the WHS, but why not call Muiden fortress simply Muizenfort if it's only this fort?

i'm pretty sure Muiden fortress also includes the great sea-sluice, the barracks, and maybe some smaller constructions.