How to access seat-post lever on the handlebar? I would like to change the position of my seat-post lever but in order to do so, I have to untighten its screw.

The problem is that I can't manage to access the screw, due to the presence of the hard metal cable going to the lever: it's right over the screw!

Here is a picture:



So here is my question, what's the type and size of the screw? How to access it?
In my line of work as well as on bikes, a cut down Allen key can be very useful. A dremel or good hacksaw applied to the short end of the tool can be used to make it even shorter, just be sure to tidy up the cut. 

In your case the long end of the Allen key could then stick out at about 10 o'clock (in your picture). You'd only get around 1/6 of a turn at a time but that's OK.

Another useful tool (though not always a good idea on tight screws) is a ball end Allen key. A set is well worth having. These allow you to drive the screw without the tool being among the screw axis, so once the screw is slightly loosened with the cut down key, you could easily take it out with a ball end key.