How to add "Edit Shortcuts" icon to Wordpress customizer
These are called 'Visible Edit Shortcuts' in Customizer Preview. You should read more about it here:
https://make.wordpress.org/core/2016/11/10/visible-edit-shortcuts-in-the-customizer-preview/
It's an extension of the selective refresh:
$wp_customize->get_setting( 'blogname' )->transport = 'postMessage';$wp_customize->get_setting( 'blogdescription' )->transport = 'postMessage';$wp_customize->selective_refresh->add_partial( 'blogname', array( 'selector' => '.site-title a', 'render_callback' => 'twentyfifteen_customize_partial_blogname',) );$wp_customize->selective_refresh->add_partial( 'blogdescription', array( 'selector' => '.site-description', 'render_callback' => 'twentyfifteen_customize_partial_blogdescription',) );Where the render callbacks call bloginfo( 'name' ); and bloginfo( 'description' );
https://make.wordpress.org/core/2016/02/16/selective-refresh-in-the-customizer/
Also check out the official Customizer documentation
So basically if you had the selective refresh in your customizer, these will appear by default ;)