So I don’t fully understand your question but here are two answers:
-you want to make the trees disappear when you “don’t see” them, well the engine handles that alone
-you want to make the tree disappear when thy are in front of you/near, well it is rather simple,
set up a trigger volume,
open your level blueprint,
Call the event “OnBeginOverlap” of the volume,
create a reference of your meshes in your level blueprint,
create a node “set visibility” for the meshes,
connect it to the Event,
set the visibility you want -> when your character will walk in the volume they will disappear.
Make the same for “OnEndOverlap” but set the visibility to visible and here you are!
No no no just put a trigger box in your level and then follow the steps I gave you.
If you find it blurry or if you really do not see what I told you to do, then look at some tutorials about blueprints on yt, trust me it will help you