The nav bar on my Elements site has got stuck in the down position…
Just clicked to open the Navigation bar and now it won’t return to the closed state. Restarting the app has not fixed it.
What can I do?
You have preview set to on in the menu controls, just scroll through the controls on the right, click on your menu to bring up those controls
Clicking on the navbar doesn’t activate any settings. The preview is sitting on top of the Menu bar so it’s not possible to select the settings for the Menu Bar 
Just realised that I can activate the Menu from the Page Layout node browser. Here I can switch off the preview. Crisis averted!
Great stuff, glad you got it figured out 