Not sure if there's a reason this isn't implemented so I'll just post it and if there is, you can let us know lol.
Please allow us to double click the Custom Code in the Overview pane in order to open the code windows for it, just like in the Preview pane which works fine there. I tend to use the Overview pane much more than the Preview pane for element manipulation and would really love to be able to just double click rather than having to right click and choose it on the menu. Would just be a much more convenient setup. :)