Since Spotfire 7.5 most of the Web UI controls for the Text Area (specially DropDown List) have been replaced for "Custom elements using divs" instead of using standard HTML elements like before (select HTML Element). So, now you don't have the change to use JS to modify for example labels and so on.
I understand that his kind of changes are not hte best way to modify the behavior but it was the only way to do that on the previous versions when you need to change things that only work on the UI layer. For example:
Change (None) label for a new one that the customer wants.
Change the background of the DropDown List when you select some special option.
So, the idea is to have more flexibility when you are working with the UI controls. I think we should recover that tool that we have before and work well to solve problems the customers have and it was flexible to provide custom solutions to do things that are not allowed by default by the customer.
We should unleash this power that is going to make greater the analysis and the tool overall.