This would be a useful feature for the CLI, as well as any GUI. Currently, the storage settings are specific to each job. A storage can have a name, but that name is still “local” to a specific job. This means that, in the fairly common case when several jobs use the same storage (such as when creating a separate “restore” job), you have to re-enter the storage settings for each job. This is especially frustrating setting up storage requires sensitive information (like API keys) that might be hard to find.
It would be nicer if storages, like jobs, were “top-level” objects that only have to be set up once per computer, rather than once per job. Then, when creating a job, users would reference one or more existing storages by name - or, in the GUI, choose them from a pop-up menu or similar.
As an added bonus, this can simplify the common situation where multiple devices are backing up to the same storage. If the list of storages was kept in its own file in the .duplicacy folder, then you could presumably copy that file and the keychain file between devices, thus setting up storages only once for use on multiple devices.