One of the most overlooked aspects of the macOS is Finder operations. The Mac Finder has been around for so long, much of what it can do is taken for granted or just ignored. One of those Finder capabilities is being able to access a covered Finder window.
There are times when you have one Finder window on top of another Finder window or you have another App window on top of a Finder window. Here is an example with Safari and a Finder window.
If you need to have to top most application window remain open and to the front, but need to move the Finder window behind it, just hold down the Command Key ⌘. Then drag the Finder window wherever you need it.
In this case, I held down the Command Key ⌘ and moved the Finder window to the left a bit to be able to read a name.
Obviously, this is not a giant deal. It can be a convenience thing if you want to avoid moving away from the window that is in “Focus”, the window on top.