Configuring dropdown menus on the data titles of bar charts (Stacked by, Split by etc) is a pain. I typically have about 50-60 columns of data, mostly category types, and I must laboriously turn off all of the fields (ie unset "Show"). I'd like to be able to select "None" (ie unset all, show none) and turn on the 3 or 4 items I want to expose.
Another vote for this one! We have many tabs with graphs on, and reducing every x-axis and y-axis drop down list to just a couple of visible options is a long process. Starting with "none" would be a huge help.
Starting from 2.7 build b117, when you click the customise spanner button, a new option called "Hide all" should become available. Clicking on this option will result in all fields to hide in the dropdown.