Feature summary (what you would like to be able to do and where):
Wikibase.cloud users would benefit from the ability to import a set of items and properties that have been exported from another wikibase (via an XML dump). This can be done on self-hosted wikibases via Special pages > Import pages, or via command line root access described here: https://www.wikibase.consulting/transferring-wikibase-data-between-wikis/ This functionality is not enabled in wikibase.cloud, however.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
I have a wikibase.cloud database that I want to bulk update using quickstatements. However, I am not sure that the procedure I have in mind will work. If it fails, I'll have to undo a bunch of edits. What I want to do is to put my existing db in a sort of sandbox (by creating a new db in wikibase.cloud) and try out my edits on it, before editing the source database itself. To do so, I need to duplicate the source database.

Benefits (why should this be implemented?):
Wikibase.cloud is set up to support experimentation, which is great. This would enable further experimentation without worrying about breaking an existing functional wikibase.