I figured out how to get split panes last night:
command+shift+P to get the command palette and then type split and you'll have options for various splits.
This will split the current file to view it at the same time in multiple views, which can be useful in it's own right but I generally prefer to have multiple related files open at the same time so I just use this to get a new pane open and then while a file is selected, any file you click on your project nav will open that file in that pane.
It would be nice to have the panes setup before opening files.