Thank you for this request.
We are planning to add custom fields to a list level and when we do you will be able to add a custom field for description to every list.
I will raise the priority of this feature internally but still cannot promise when it will be implemented.
There is already a PITS issue for this but you have already voted there. If you want to add more comments please, follow this link: http://www.telerik.com/support/pits.aspx#/public/sitefinity/6168
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