If there are pre-existing renders in the Render destination path, you are prompted to either Cancel or Replace the pre-existing media.

The steps marked as Baked are included in the Flare render whereas the steps marked Soft are applied live in Lustre on this new "source."
You can continue grading, on top of the rendered effects, using any of the stages of the Lustre pipeline that remain ‘Soft’. At any point, should you want to add more effects to your shot, click the “Edit” button under the Batch toggle to send the latest Lustre grade to Flare and automatically update the Batch Setup, while preserving the effect that was already built. BatchFX behave a lot like other aspects of a Lustre grade and may be copied from one shot to another and saved in the Grade Bin.