It's not possible to completely disable copy subtree via copy_subtree.limit.

Ref. https://doc.ibexa.co/en/3.3/extending/config_back_office/#copy-subtree-limit

Steps:

1. Set in config/packages/ezplatform_admin_ui.yaml under system.admin_group:

               subtree_operations:
                   copy_subtree:
                       limit: 0
   

2. Reload cache.
3. Check behaviour in admin UI content structure.

Actual result: Copy subtree is enabled (except root and default limit).
Expected result: Copy subtree is disabled globally.