One user (Alice) has made a private collection of releases. The second user (Bob) was added to this collection as a collaborator. Bob can view the the private collection of Alice. It is also possible for Bob to delete releases from Alice’s private collection.
Bob wants to add a new release to the collection of Alice. The private collection of Alice doesn't show up on the list of collaborative collections on the right panel of a release. The same problem occurs if Bob wants to delete a release from this collection.
However, the private collection of Alice gets shown if Bob clicks on the list of other collections.
If Alice sets the collection to public the collection shows up in the right panel of the release and it is possible for Bob to add and remove releases to/from this collection.
The private collection of Alice should show up for Bob as a collaborative collection when he browses releases. Bob should be able to add and delete releases to/from this collection.