Add new dashboard widget

Source: 10+ Useful WordPress Code Snippets

Remove Posts menu for Editor, Author, and Contributor

Source: 10+ Useful WordPress Code Snippets

Remove Items from admin bar for authors

Source: 10+ Useful WordPress Code Snippets

Remove Edit Title, Add new, Permalink, View Post buttons from Custom Post Type Edit Screens

Source: 10+ Useful WordPress Code Snippets

Remove editor only for author based on Custom Post Types

Source: 10+ Useful WordPress Code Snippets

Remove Dynamic Widget Metabox from Custom Post Type Edit Screens

Source: 10+ Useful WordPress Code Snippets