You can use the Activity Monitor in Lytro Desktop to view the current processing tasks. You can pause or cancel tasks individually or all at once using the Activity Monitor.
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 give you the option to cancel operations. For example, here's the activity monitor while exporting an animation as a movie:
Click "cancel" to cancel an individual task or "Cancel All" to cancel all currently processing tasks.
NOTE: Closing Lytro Desktop after hitting pause is the same as canceling all operations.