Can you share about your use case, how will you use the temporary blurring? Similar things have been done when people want to show off their vault, but since you use temporary blurring, it raises question how you are going to use it. You can input foldable callouts which are very similar to your use case, but the difference is that show/hide requires a mouse click or Fold less/more command. There’s also Fold all headings and lists and Unfold all headings and lists commands. Mouse hover based formatting is in general problematic since it adds unwanted visual flickering to your editing experience.