The Entries[Remove] command removes all references to an entry from the context menu for the current session.  The effect of this command is not permanent unless you save the menu to a repository using ContextMenu[Save].

The parameter action specifies the action or actions to remove. If action is a string, any entry in the top-level context menu with this name will be removed.  If action is a list of strings, this is interpreted as a hierarchical sequence of submenus starting from the top-level menu.  Any menu entries whose submenu entry sequence begins with action will be removed.

with(ContextMenu[CurrentContext]):

Remove the top-level menu entry that negates a boolean value.

Entries[Remove]("Negate");

Remove the submenu entry that sorts a list in ascending order.

Entries[Remove](["Sorts", "Ascending Order"]);