Hi,
Because of the way how several processes are optimized (like the Camera - Limit to visibility feature), the highly recommendable way would be to use the Custom Edit mode for the final render. All its parts and the Forest object itself can be linked to a helper object while building the scene, but as mentioned previously to avoid any sudden changes in the distribution and correct functionality, it should be switched to the Custom Edit mode before the rending process (this change is reversible).
Best regards,