There is an Amazon FBA fullfilment provider integration for the UK. However after Brexit this doesn't work anymore to send items to Europe. I would suggest that this integration was extended to Germany so I can send product to customers in Europe.
For anyone on the Shipstation team reading, I see this not as a 'nice-to-have' feature but as a 'start-researching-other-platforms' feature. Europe is a key part of our growth strategy and not being able to fulfill orders to customers in the EU through Shipstation when we already have inventory in the EU (that we've paid several years' worth of Shipstation subscription to buy, ship, and clear customs on) is a brisk push to other platforms. When I submit this reply, I'm going to start researching other platforms after 3 years with Shipstation.
My understanding is that FBA Italy/Spain/France/Germany formerly integrated with FBA UK and comingled inventory, but now Brexit has forced separate registrations throughout, and inventory doesn't flow seamlessly across those borders anymore. A separate integration was not formerly needed, but now it is. Maybe I'm totally off, but if I know anything about the internet, the best way to find a right answer is to confidently post a wrong answer.
I am confident that I am correct on this.