SFTP protocol supports custom file attributes, and this looks like a useful feature. However, in order to use this, support at both the server and the client would be needed.
An error occurred while saving the commentAdminRebex (Admin, Rebex) commented
The SFTP protocol actually supports custom file attributes (and it also supports custom protocol extensions). However, in order to use this, both the client and the server would have to support this feature. But it does indeed look like a very interesting use case and we will consider adding it. Are you going to use Rebex SFTP at the client as well?