In this POC, the user can select 'Main content', revealing a context menu. They can open up the properties of this element by clicking the cog icon in the context menu, or using the keyboard shortcut Alt + M to open the properties menu. In addition, the side navigation can be clicked to toggle panels open and closed. Using this POC greatly helped users understand the proposed functionality and gave them a chance to test it out before it was implemented.
See the Pen Sidebar + panels with keybinding by Samantha Howes (@dusterbed) on CodePen.