This category lets you link a project against any object file or library, regardless of the filename.
The file-selection dialog may seem slow when adding new files. This is because the system can't make assumptions about naming conventions and instead must inspect a file to determine if a file is an object file or a library.
The Extra object files option is available for an individual platform only. If a project has more than one active platform, you can't use this feature. In that case, you can still specify extra object files using the Advanced mode for each platform separately.
The default dialog for the Extra object files category.
Field descriptions for the External object files category