SplitPane under header while still using SideMenu

I got a blog posting notice about SplitPane so I thought I would revisit an unanswered question.

How does one implement a split pane under a main header while maintaining the SideMenu functionality?
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This can be achieved with CSS but attempts to do this with the new SplitPane have not worked. Often either the SideMenu contents or the main pane contents are un-clickable.

This is intended to be used on phones and in browsers.
Is this an option or should I stick with CSS to achieve this?

The question was partially answered here but did not implement the SideMenu and some items were not clickable.