I’m trying to add an item to my menu but when I click on "add item" the secondary toolbar slide-out section is hidden underneath the primary one. I just updated to WP 4.8 but it’s still happening. Here’s a photo of what’s going on:
I figured out a solution, to edit the menu from the dashboard, instead of the site.
At any rate, you can always fall back to the Appearance > Widgets or Appearance > Menus panels in the dashboard. To be honest, I still prefer those panels. 🙂