This is such a good idea. This is something I am definitely missing from Roam as well, in the sidebar. When you shift-click load multiple documents into the sidebar, you end up with a single pane full of multiple documents that you can reference and edit seamlessly. And remove documents from the queue when you are done with them.
This is very different than splitting panes. When you are splitting past 3 or 4 documents, you can end up with a huge amount of headers, and you can’t scroll them all together in one contiguous view, like Scrivenings.
This contiguous, seamless view is amazing for synthesizing ideas from multiple documents into one. It is also great for loading up a queue of unrelated documents you want to edit, without a huge cluttered multi-header split.