Large »Custom Field« Textareas.
Gladly those are easy to target. Wrapped up in a small plugin:
<?php
! defined( 'ABSPATH' ) AND exit;
/* Plugin Name: (#65922) »kaiser« Bigger custom field textarea */
function wpse65922_big_customfield_textarea()
{
?>
<style type="text/css">
#the-list textarea,
#newmeta textarea {
height: 200px;
}
</style>
<?php
}
add_action( 'admin_head-post.php', 'wpse65922_big_customfield_textarea' );
add_action( 'admin_head-post-new.php', 'wpse65922_big_customfield_textarea' );
This targets the existing as well as the new custom fields textareas.
Go Fullscreen (built in) for the WYSIWG editor
Since some time, WordPress got the “Fullscreen” Mode. Just click it and the textbox expands to the whole screen, so you can write distraction free.