When right-clicking on a project and select "Add Files...", the only question asked is "To which targets does this file belong?" No further details are asked when adding files to a project. Do libraries require additional information?
For drag-n-drop, the most useful would be to have a normal (left-mouse) drag automatically apply the dragged files to all targets. For the more specialized files (debug, platform-specific, etc) one could have a right-drag that would call up the file properties dialog on completion of the drag-n-drop operation. Right-clicking a file is already in the current build, and brings up the properties, where the the build targets can be (de)selected.