Как сделать фиксацию и пролистывание кнопки "добавить"?

$body_class = "";

$body_class = "dle_theme_dark";

$body_class = "dle_theme_dark";

$body_class = "dle_theme_a";

$body_class = "dle_theme_b";

$body_class = "dle_theme_c";

$body_class = "dle_theme_d";

$body_class = "dle_theme_e";

$body_class = "dle_theme_f";

$body_class = "dle_theme_g";

$body_class = "dle_theme_h";

$body_class = "dle_theme_i";

$body_class = "dle_theme_dark";