Good news. The latest Classic Shell 4.0.6 has a built-in button now to toggle the folder/navigation pane as well as the Details pane and the Preview pane.
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See this thread: https://sourceforge.net/projects/classicshell/forums/forum/1049755/topic/3932317
Good news. The latest Classic Shell 4.0.6 has a built-in button now to toggle the folder/navigation pane as well as the Details pane and the Preview pane.