When you scroll in Vector with VE enabled, the toolbar will be fixed to the top of the window if the toolbar reach it. This works fine, when you have a skin without a fixed header, but some skins have a fixed header, so the VE toolbar is (maybe partially) hidden by a fixed element. This could be solved by implementing a configurable offset (e.g. using a JS variable, which isn't set in VE, but can be set by any extension/skin), which can be set by skins, that need it. This would be one step into the direction to support more skins.