When you save a container to be referenced later, you can lock the containers so that only their published attributes can be manipulated in the parent file. Additionally, you can lock the file itself so that no reference edits can be saved to the file from a parent file.
Locking is important for referenced containers because changes made to the unpublished attributes are invisible at the container level. Likewise, changes saved to unpublished attributes are lost if the referenced container is replaced. Locking ensures users use published attributes so as to avoid these pitfalls.
To lock unpublished attributes for referencing
Make sure to publish any attributes that are needed by the parent scene.
This prevents users from saving any reference edits to this file from the parent file.
When the file is saved, all the unpublished attributes for all containers in the scene are locked. This is the equivalent of selecting Assets > Lock Unpublished Attributes for each container. Users cannot unlock these attributes from the parent file. For more information, see Lock a container.