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The main difference between the old and new implementation is that a user is no longer created for external shares. In stead Instead the share impersonates the owner of the collections when the assets are accessed via a sharing token (link or e-mail).
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More sharing options
Link (External)
Groups (Internal)
Expiration date for all shares
Revoking a share
Overview of who it is shared with
It is no longer possible to remove of a shared collection from your collections page.
For more information and a migration path, see the following documentation