If you find the post editor’s optional excerpt textarea field size to be too small for your liking, you can easily adjust it’s size to make editing easier. I make heavy use of the excerpt field in WordPress. If the excerpt textarea field is left empty when publishing a post, the default WordPress action is to show the first 55 words of the post’s content (if the_excerpt() is used in place of the_content() in templates.) I prefer to specify my excerpts by making use of this field but have found the default textarea size to be much too limiting.

Adjusting the textarea size can be done without plugins and without editing core WordPress files.

Instead, we’ll make use of the functions.php file in the theme directory (wp-content / themes / yourtheme). If there is no functions.php, don’t worry. Just create a new file with this name in your theme folder. Add the code below to the file somewhere between the <?php and ?> lines. If you had to create the functions.php file, simply add <?php to the beginning of the file and ?> to the end (note! do not add a line break at the end of the file).

 function admin_excerpt() { echo "<style>"; echo "textarea#excerpt {height:200px;}"; echo "</style>"; } add_action('admin_head', 'admin_excerpt');

Customize the textarea size by changing the number 200 in the code above.

The functions.php file basically acts like a plugin, and if it is present in the theme you are using, it is automatically loaded during WordPress initialization (both for admin pages and external pages).

References:
Click to visit this external linkTheme Development, Click to visit this external linkTemplate Tags, the excerpt

HTH! Did it work for you?