I have been investigating Liquid Glass and hit a similar issue with the leading navigation bar items. In a simple project (that I haven't been able to find a simple place to upload), if I have one view controller with a leading navigation bar item that has .sharedBackgroundVisibility(.hidden) set and then push on a second view controller, there is a visible white rectangle shown inside the back button during the animation. So far I have not been able to find any kind of workaround, but this significantly limits the ability for us to customize the content shown in the header.