We provide preview panels for color & fonts settings, as well as for formatting options.

Usually, the preview panels contains most of the code constructs that you are trying to customize. But in some cases
(for example, for the formatting options) you have to scroll down to see some of the changes you are making, and in
other cases, you are customizing the color for something (say regular expressions) which aren't present in the code sample.

There's a trivial solution for this:  Make the preview panels editable!!  Whenever the user switches to a new language
or formatting category, they get the default text.  But they can replace this text (or insert/edit it) to contain
whatever they would like to see in the preview. (I don't think we need to over-engineer this and try to make it
persistent - it's just for quick explorations of the results of a change).

Also, to make this possibility blindingly obvious, we should insert a label below the text preview area which says "The
above code sample is editable!" - or we can just edit all the code samples to have their first line mention this.