Everytime I go to the save/load menu, DC is activated (first time in each session I think). Why is that? Can it permanently be disabled?

Hello, how do you mean activated? Do you have a screenshot from your KIA options screen to share?

Edit (correction!): In fact, the normal state for it, when you start a new game (from the beginning) is to be de-activated.

Could you share a screenshot just to be sure of the issue?
What is the platform you're playing the game on?

Can anyone tell me what this option do? I cant seem to find nothing about it in manual...

It generally does not affect much.
When the "Designer's Cut" is enabled certain lines of dialogue are removed, some lines from McCoy's inner monologue and this is mostly in Act 1.

This is after loading my savegame "05" and pressing Esc (see attachment). I'm on Win 7 x64. I may have accidentally activated it before saving?

Yes, I was wrong before, sorry for any confusion.
The state of the DC option is saved with your saved game.

If you had enabled it before saving, its state is saved with your save-game and it will be set as enabled when you load that particular save game.

And if you disable it and create a new save game, then loading that one will have the DC option disabled.

Starting a new game (from the beginning) should have the Designer's Cut disabled always.

Thanks for clearing that up! :-)
You're very helpful; are you related to the project somehow?

I am part of the ScummVM team, one of the core four developers that work on the Blade Runner engine.

We appreciate all feedback, and bug reports.

Hip hip hooray! And thanks for the great work!

WORD. I am very pleased so far.