I have an idea for a new folder type that would be especially useful on mobile devices, or any devices with limited storage. the basic idea is that the folder would actually try to not store files locally, except temporarily.
here’s how i envision the feature working:
when the folder is added from a shared device, it behaves like the all files are set to be ignored and doesn’t download them
the global directory tree is available to the user in the interface, and the user can choose files to not ignore, and be downloaded.
default behavior for new files found to exist locally would be for them to be synced to other devices, but unless/until they are flagged to be kept locally, they are set to ignore and deleted from the local storage once they are uploaded (ideally, it would be configurable to set an “exists on n other known devices” criteria before delete, but i don’t think that information is currently available to query. also probably a “keep new files for at least x minutes” before delete.)
If the option to query “exists on n other known devices” were available, it could provide a means for a “distributed storage” mode too, where devices could be set to retrieve otherwise ignored files if their minimum replication threshold value wasn’t being met after a grace period, and local copies could be deleted to free up space if the number of copies available globally were over a maximum replication threshold this could be used to create a way to store files redundantly across multiple systems without having copies of all of the files on all of the systems.