The Activity Monitor
When Lytro Desktop is busy doing something, you'll see a spinning disk in the Activity monitor section.
Clicking on the spinning disk will reveal activity specifics, and gives you the opportunity to see progress and cancel operations. For example, here's the activity monitor while exporting an animation as a movie:
You can pause any operation if you need extra computing power, or cancel if you don't want to wait for the process to finish via the 'll' and 'x' buttons to the left of the progress bar.
NOTE: [Windows] Hover the mouse over the progress bar to see the pause and cancel buttons for that process.
NOTE: Closing Lytro Desktop after hitting pause is the same as canceling all operations.