backend_sidebar
Adds custom content to left-hand sidebar.

Blog
Input (passed by reference)
No specific parameters.
… your plugin code …
Output
{$backend_sidebar.menu}
Custom LI element in top menu, next to “All posts”, “Comments”, etc.
{$backend_sidebar.section}
Custom section next to “Blogs”, “Drafts”, etc.
{$backend_sidebar.system}
Custom LI element in bottom menu next to “Settings”, “Pages”, “Design".
Blog
Plugin code example
PHP
public function backendSidebar() { return [ 'menu' => '<li><a href="">' . _wp('Top section link') . '</a></li>', 'section' => '<h5 class="heading">' . _wp('My sidebar section') . '</h5> <div class="box"> <ul class="menu"> <li><a href="">' . _wp('Link 1') . '</a></li> <li><a href="">' . _wp('Link 2') . '</a></li> <li><a href="">' . _wp('Link 3') . '</a></li> </ul> </div>', 'system' => '<li><a href="">' . _wp('Bottom section link') . '</a></li>', ]; }