Allow users to collapse shelves together

[rektide]

The work here should include efforts to allow users to share data among shelves.

For one example, as a user, I don't want to carry a series of WebBundles from a trusted provider with me that each end up on their own shelf. I want my shelves of content to work together neatly. I have gotten a series of resources that I now carry with me, but because of this specification, they are each their own fragmented, disunified, separate experience, and I the user have no option, no capability to bring the data that this specification has broken apart on different shelves back together.

[asutherland]

Note that I'm extrapolating from the use case "The work here should include efforts to allow users to share data among shelves." something like https://unhosted.org/ in terms of the goal of shared client side storage without involving a server.

You may want to take a look at the (Multiple) Storage Buckets WICG Explainer and File System Access WICG Proposal if you're not already familiar.

The most likely UX experience that would allow users to provide informed consent to shared access to data across origins would be an <input type="file"> picker-like experience where the user is explicitly choosing to provide a grant to a shared resource. The File System Access mechanism uses this approach, for example. One might imagine that once we've standardized multiple storage buckets that a similar mechanism could be used such that an origin creates a bucket marked as shareable, the user could provide some kind of consent to expose this to the local picker list, and then subsequently the bucket becomes accessible from a picker triggered by another origin.