I know resurrecting an age old thread, but I sort of bumped into something simliar:
I am trying to get a welcome screen (as the initial view), that is just a normal page: no splits, whatsoever. When the user clicks on “Get going!” to start to use the app (a PWA actually), they shall be presented with a split view with a toolbar on the left/right (in panel, that hides on mobile, hence the split requirements), and the rest of the content in the main view.