Allow me some time to look into and try and reproduce this. In the meantime can you confirm that Qt Design Studio itself is properly installed and working on your Windows machine on it’s own? Also if possible can you locate where the binary/files for Qt Design Studio were installed on your machine.
Ahh okay I was able to reproduce this on my setup I think I know what went wrong. So you don’t need to set the path all the way to the bin folder just to “C:\Qt\Tools\QtDesignStudio”. The extension expects to be in the QtDesignStudio folder.
In order to change the path go to the extension menu in VSCode right-click the Qt DesignStudio Support extension and change the path in the extension settings.
I’ll see to this being documented more clearly in the future.