I made a level editor once, for a game project that has been halted for a bit...
The editor saves a 8 x 10 level made from a tile set.
The interface is very crappy, there's no feedback
It basically stores different types of rooms, so you design the room by clicking the tiles and dragging the level. Then, you type the number of the room you want to save and press "save"... You can repeat this to every other room. When you want to save your levels, you just have to press "Publish" - it will save a text file on the same folder of your .cap. To load the levels again, restart the level and press open. Then, type the numbers you want to load and press "load".
Well, since this was a prototype, I wasn't trying to make it functional yet. But the whole saving/loading works very well!
If you need any additional advice, keep on asking! I don't know how familiar you are with Construct, but these events should be hard to understand.
EDIT**
Oops I forgot about the scrolling thing.
The System events have a "Scroll to X" and "Scroll to Y", and you have the ScrollX and ScrollY values too. So you can easily do a:
* "X" key is down ---> System: Scroll to X - ScrollX + 10
Voil�!