We have various users that save tasks as drafts in Forms. When they save as a draft they want to be able to add a comment, which we can technically do by adding a field to the form, but they want to be able to show the draft comment as a column in the Inbox. This could get complicated if you allow adding any field as a column in the Inbox, so my thinking is what if when you click Save as Draft it prompts you for a comment (not required). Then it would be a system value, not specific to a process and could easily be an option to add as a column to the Inbox.