Michael Adams (mdawaffe)

Just One Category will cause WordPress to display on a category archive page 
only those posts which are direct members of that category, i.e. this plugin 
will exclude from that category page all posts which belong to any of that 
category’s subcategories but do not belong to the category itself.

Just One Category

On a category's archive page, displays only the posts directly in that category, not in any sub-categories.

Hung Trang Si

Plugin help hide all posts in one or more category on your homepage.
Go to “Settings » Reading”to choose the category need to hide

Simple Exclude Categories

Hide posts in categories on WordPress Homepage

Just One Category vs Simple Exclude Categories