If you just start typing 'block' into a layout, then you are prompted to enter either a 'block if' (i.e. a conditional block) or a 'block' (e.g. a PHP block or a list block). Either way, the closing '/block' tag is added into the HTML at the same time.
Hope that's useful.
Also, the black lines in the left margin of the code edit do show the start and end of a block expression (as long as the opening and closing ones are on different lines)
Sorry chris, didnt make myself clear. I meant that when I have a lot of blocks on the page it would be good if it would remember if I have minimized them or not. For example, I have quite a lot of block ifs that once I set up I never need to see, but as they are all open it lengthens the code somewhat.
Comment