Seamless Mode Windows 10

[Compaq]

I am running OpenSuse Leap 15.1 as the host and Windows 10 Pro as a guest. If my guest operating system Windows 10 switches to Seamless Mode Host + L, only windows that are not integrated Windows applications are displayed correctly. The taskbar disappears when, for example, I click Start. Windows windows are only visible if an application that is not provided for Windows is open on the desktop and serves as a background. My VirtualBox version is 6.1.18 r142142 (Qt5.12.7). Guest additions and the current Extensions Pack are also installed. As a guest I also have a Windos7 Pro operating system and everything works perfectly!