What's the option for? The menu title would suggest that there is a way to export a player-created character that could be imported into a campaign but as far as I can tell there is no way to export a character.
Never mind, I see that creatures can be exported from Game Master mode and imported into Game Master campaigns. I hope that a capability to import/export player characters will be added in the future.
This option allows you to "export" any character/item from game field to later use in that game master campaign. For example if you created combat encounter with a "special" boss like creature and you want to use it few time more in other scenes/situations - you can export it and spawn it from the panel whenever you need. This should save you time for quickly accessing some notable items or monster through your campaign