Back-end Order Links Should Exist for Rakuten
You already support hot-linking the store-specific order number to the back-end of the marketplace for Amazon and ebay. Possibly others. Rakuten should have this benefit too. There is a reliable URL prefix that just needs the order number appended to it to construct a link. Attached is an example of one of the few places you may see a link.
The order number prefix would be https://rmsportal.rakuten.com/orders/details/view/
I'm not even sure I should burn my votes on this, as the idea is not new in general, you just haven't completed it when possible on the marketplaces you officially support. What I would actually use more votes on is if you let us configure this per-store, so that we can pick up the slack.