How can I remove the search window?

I searched through all the files in the theme for the word “search” and tried removing that command from entry.php and entry-summary.php. None of that had an effect. I also tried removing the search.php file, that had no effect.

To save you grief, any edits to the core files provided by WordPress will potentially break your website if you modify it incorrectly. Also with each new update provided by WordPress, it will overwrite and re-add the files to their default/updated state.

To hide the search, add the following to your child theme’s function.php:

add_action( 'wp_before_admin_bar_render', 'wpse_254662_toolbar', 10, 1 );

function wpse_254662_toolbar() {
    # Hide search from admin toolbar
    global $wp_admin_bar;
    $wp_admin_bar -> remove_menu( 'search' );
}