There are two ways to use this mode in Windows 10. Either click on the Task View icon on the task bar (shown below and highlighted in red), or press the Win-Tab keys simultaneously.

Use Task View: Press Win + Tab to open Task View and check if you can manage your desktops there. Sometimes, the issue might be with a shortcut or the way you are accessing the feature.

Whether you have Windows 10 or Windows 11, there are features embedded that can be put to good use within Task Manager. It's no longer just for getting things that weren't working to stop trying ...