How to add new columns into bookmarks?

Hello, I have a dashboard where there are 5 public bookmarks ; 4 created by another user & 1 created by me.As per our new requirement i added a column into our report.When the user clicks on his bookmark, he is not able to see this column in the filter panel because the previous view when he saved this bookmark it does not exist. Now for the another user to see this column , should he -Delete his old bookmark and create a new one with this new column? or is there another way?. Because deleting all these 5 bookmarks are re-creating will be a lengthy process. Secondly, why am i not able to update public bookmarks create by him, me being the developer should be able to control all the bookmarks in my dashboard correct? Regards Raghav