Slide 1

function my_avf_customize_heading_settings( array $args, $context, array $extra_args = array()){
  if( 'avia_slideshow' == $context ){
    //  get class of slideshow
	  $slider_class = get_class( $extra_args[2] );

		// selection array are:  'avia_sc_slider', 'avia_sc_slider_fullscreen', 'avia_sc_slider_full'

		// example is here Fullwidth Easy Slider
	  if( in_array( $slider_class, [ 'avia_sc_slider_full' ])){
		  
		  $index 	= $extra_args [1];
		  $attr 	= $extra_args [3]['attr'];
		  
		  // if heading_tag is default (no custom choice) and is slide No.1
		  if( $attr['heading_tag'] == '' && 0 == $index ){
			  $args['heading'] = 'h1';
		  }
		  // if heading_tag is default (no custom choice) and is slide No.2
		  if( $attr['heading_tag'] == ''  && 1 == $index  ){
			  $args['heading'] = 'h5';
		  }
		  // if heading_tag is originally set to p-tag (custom choice) - and we want to change those to  h3-tag
		  if( $attr['heading_tag'] == 'p' ){
			  $args['heading'] = 'h3';
		  }
    }
  }
  return $args;
}
add_filter( 'avf_customize_heading_settings', 'my_avf_customize_heading_settings', 10, 3 );