When I export projects as CSV, every single custom field always appears in the export, including old custom fields that I’ve since deleted from the project, so long as there are tasks that have values in those fields. I’d love to be able to determine which custom fields appear in the CSV, so I don’t have to do a bunch of cleanup in Excel every time I export.
My proposed solution is this: when you click Export > CSV, a new dialog box pops up with a list of checkboxes representing every column that would normally appear in the CSV export (i.e. all the custom fields I’ve added to the project plus all the default fields like due date, assignee, completion date, etc). I can then check/uncheck the boxes to show only the columns that I want to have in my export. An added bonus would be if I could save a particular set of selections as a “saved custom export” or something so I can just run that instead of checking/unchecking things all over again the next time I want to run the export.