Removing and/or updating Signs

Hi. I've read the PDF and searched the forum but I still don't get this right. I'd like to be able to update and/or remove Signs so that in-game dialog boxes doesn't stay the same throughout the entire game. Just to clarify, in one room there's an NPC with a sign and I only want this to pop up during the first visit. In another room there's another NPC with a sign and this one I'd like to update so that it says something else upon the second visit to the room.

Is there some kind of functionality for these kind of features in the KS Level Editor (or 3rd Party) or am I supposed to work around this by creating Shifts that leads to and from clone rooms without the Sign or with the updated one and so on? I'm not bashing the KS Level Editor if that's the case but I only begun creating KS levels yesterday and I would be a little bummed if I made such an advanced setup and it turned out you could simply tick a box or something. 

you can't change a screen's content ingame, you'd have to use shifts and flags.

Ok, I'll look closer at those functions then. Thank you very much!

Yeah, you'll need shifts/flags or warps for this.

If you can design your level cleverly, you might get it entirely with warps.

The best way in original KS is to use warps or flags. In KS Ex you can do these things with a script, like I did in the Ball Tutorial. There I have 9 different sign texts in one screen (A through I ) and which one is displayed is determined by powers the player has.