The idea behind writing the ChartEditor demo was to demonstrate how a relatively simple GUI for user-editing of the most important properties of TChart and related components could be created. The emphasis is on "most important", not "all". An extremely complex GUI for chart properties is that of Delphi's TeeChart which addresses "all" properties, but has a pagecontrol inside a pagecontrol inside a pagecontrol inside a pagecontrol inside a pagecontrol - that's was not my intention.
In the current implementation of the demo the user can only hide the frame and change its color. I consider these to be the "most important properties" here. With your patch the entire user interface would become inconsistent. Why can I change the pen width of the legend, but not that of the title, footer, axis title, axis labels? This calls for applying your patch also to these chart elements. With every newly added feature the demo will move away from the original intention and approach the dialog of TeeChart.
Therefore, I will not apply your patch to the demo. Sorry to disappoint you, but if you need the feature add it to your local copy in your project. As I can see from your patch you understood the basics and can easily extend it.
BTW, once the storm related with the svn-to-git transition has settled down, I am planning to write a tutorial about the ChartEditor demo to explain the basic elements and to show how new features could be added.