When "Always Show Toolabar When in Full Screen" is turned off, the sidebar is open, the text input into the URL bar is activated, and the cursor is not over the toolbar the traffic light buttons in the top left overlap the sidebar and the button to select a window. It actually does happen in Safari, but doesn't seem like a Webkit thing.
I expected the window picker button to move down to accommodate the buttons.
Version 0.99.130-rc (WebKit 621.1.2.111.4)
Sequoia (15)