Batch exporting directly from Final Cut Pro X?
While there are many sharing options built into Final Cut Pro X, some folks turn to Compressor, Apple's professional compression application, for more advanced capabilities. For example: creating custom presets, setting compression markers, and batch encoding.
However, it's possible to essentially mimic Compressor's batch encoding functionality directly inside of Final Cut Pro X. Plus, if you own Compressor, you can export to any of your custom Compressor presets (or any of the built-in presets) without ever leaving Final Cut Pro X.
In Final Cut Pro X, you export your project either through the File > Share menu or by clicking the Show Share Destination icon at the far right of the toolbar. Either way, one option that appears is Add Destination. Selecting it opens the Destination window with options like DVD, BluRay, Vimeo, YouTube, Export File, and the key: Compressor Settings. Dragging the Compressor Setting destination to the Destinations list opens a window where you can select from all of Compressor's built in presets and from any presets you've created yourself in Compressor.
Once you've added this new custom destination, the next key step is to assign it as the default destination by right clicking on it and choosing Make Default. Doing so assigns the keyboard shortcut, Command-E, to this preset.
With these preparations completed, creating a batch export of multiple projects is quick and easy: simply select a project in the Browser, press Command-E, change the title and metadata if needed, and submit. Repeat each project you want to batch. They will all be queued up and start exporting in the background (you can view the progress by clicking the Background Tasks icon in the dashboard).
A further advantage to this approach is that if you have already rendered your project, and you are exporting to that same codec, Final Cut Pro will use those render files, thereby speeding up the export process. Compressor, on the other hand, always creates new render files.
On disadvantage is that, although you can continue to work in Final Cut Pro X during the export, the export process will take longer since your editing tasks take top priority.