There are a lot of ways to suggest improvements and enhancements to the GUI/UX. It would be good to have a category specific for those ideas when they are more about usability and clarity of design then the actual function being executed.
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You are able to customize your Ideas portal categories. See the last section of Create a submit only, private, or public portal.
Configure idea categories
Use Idea categories to organize your ideas. They allow your users to specify what category their idea belongs to and allows other users to browse through the categories.
Categories are configured per product under Settings -> Product -> Configure idea categories.