Don't apply transform before sessionrestored

chrome/autohide_toolbox.css

@@ -45,6 +45,9 @@
 
 :root[sizemode="maximized"] #navigator-toolbox:not(:focus-within):not(:hover){ transform: rotateX(89.5deg) }
 
+/* Don't apply transform before window has been fully created */
+:root:not([sessionrestored]) #navigator-toolbox{ transform:none !important }
+
 :root[customizing] #navigator-toolbox{
   position: relative !important;
   transform: none !important;