If I’m understanding correctly you’re looking for a split navigation. That is not a possibility. It would take a very specific stack design to pull that off. You could manually build a secondary navigation for the “sidebar” but it would not get automatically incorporated into the “hamburger” menu for mobile devices.
I have ideas for other navigation styles for the future, including one that might be a manually created navigation system, but that is far off, and I’m not sure it would 100% match what you’re wanting to do either. Sorry.
There are currently limits on the upper and lower side of the values for these heights. You cant go below 55 px or above 80 px currently. This is in an attempt to make sure the Navigation Bar’s layout looks and functions well across all displays.