Inject new array into an array at a specific position - Everything in Its Right Place: https://www.damiencarbery.com/2019/02/inject-new-array-into-an-array-at-a-specific-position/

agentpress-after-insert.php

<?php
array (
  'col1' => 
  array (
    'Price:' => '_listing_price',
    'Min Price:' => '_listing_min_price',  // Inserted element
    'Max Price:' => '_listing_max_price',  // Inserted element
    'Address:' => '_listing_address',
    'City:' => '_listing_city',
    'State:' => '_listing_state',
    'ZIP:' => '_listing_zip',
  ),
  'col2' => 
  array (
    'MLS #:' => '_listing_mls',
    'Square Metres:' => '_listing_sqft',
    'Bedrooms:' => '_listing_bedrooms',
    'Bathrooms:' => '_listing_bathrooms',
    'Basement:' => '_listing_basement',
  ),
)

agentpress-change-sq-feet-to-sq-metres.php

<?php
/*
Plugin Name: Change AgentPress Listings fields
Plugin URI: https://www.damiencarbery.com/2019/02/inject-new-array-into-an-array-at-a-specific-position/
Description: Change 'Square Feet' to 'Square Metres' AgentPress Listings fields.
Author: Damien Carbery
Version: 0.1
*/


add_filter( 'agentpress_property_details', 'dcwd_change_agentpress_property_details', 20 );
function dcwd_change_agentpress_property_details( $details ) {
	unset( $details['col2']['Square Feet:'] );
	$details['col2']['Square Metres:'] = '_listing_sqft';
	
	return $details;
}

agentpress-default-details.php

<?php
$details = array(
	'col1' => array(
		'Price:'   => '_listing_price',
		'Address:' => '_listing_address',
		'City:'    => '_listing_city',
		'State:'   => '_listing_state',
		'ZIP:'     => '_listing_zip'
	),
	'col2' => array(
		'MLS #:'       => '_listing_mls',
		'Square Feet:' => '_listing_sqft',
		'Bedrooms:'    => '_listing_bedrooms',
		'Bathrooms:'   => '_listing_bathrooms',
		'Basement:'    => '_listing_basement'
	)
);

insert-array-after-key.php

<?php
// https://www.damiencarbery.com/2019/02/inject-new-array-into-an-array-at-a-specific-position/

function insert_array( $array, $after_key, $insert_array ) {
	// Return immediately if $after_key isn't in the array.
	if( ! array_key_exists( $after_key, $array ) ) {
		return $array;
	}

	$new_array = array();
	foreach ( $array as $k => $v ) {
		// Copy key and value to the new array.
		$new_array[ $k ] = $v;
		// If we find $after_key
		if ( $after_key == $k ) {
			// then add each key/value of $insert_array
			foreach ( $insert_array as $nk => $nv ) {
				$new_array[ $nk ] = $nv;
			}
		}
	}
	return $new_array;
}


// Use it to insert 'Min Price:' and 'Max Price:' directly after 'Price:'
$ins_array = array( 'Min Price:' => '_listing_min_price', 'Max Price:' => '_listing_max_price' );
$details[ 'col1' ] = insert_array( $details[ 'col1' ], 'Price:', $ins_array );

so-change-key-solution.php

<?php
// https://www.damiencarbery.com/2019/02/inject-new-array-into-an-array-at-a-specific-position/

// From: https://stackoverflow.com/a/21299719/8605943
function change_key( $array, $old_key, $new_key ) {

	if( ! array_key_exists( $old_key, $array ) ) {
		return $array;
	}

    $keys = array_keys( $array );
    $keys[ array_search( $old_key, $keys ) ] = $new_key;

    return array_combine( $keys, $array );
}

// Use this function to change 'Square Feet:' to 'Square Metres:'
$details['col2'] = change_key( $details['col2'], 'Square Feet:', 'Square Metres:');