Hi,
To avoid any possible duplicated object(s) (having
Select Influences enabled) or the need of reassigning Custom Objet(s) while merging such Forest object(s), a recommendable work-flow would be to to build (& use for these purposes) your own Forest presets. I would suggest you to check our "
Creating Libraries" tutorial covering this topic in detail.
Hope you'll find it interesting and helpful.
Best regards,