Extending / editing a panel snippet


I am new to Kirby and I have a question about modifying something in the panel. I don’t know all of the proper Kirby terminology yet so please bear with me.

I have modified the Files snippet for the sidebar so that a thumbnail image is displayed (see image). I did this by directly editing the file located in: panel/snippets/pages/sidebar/file.php like so:

    <a <?php e($file->canHavePreview(), ' data-url="' . $file->crop(75)->url() . '"') ?> data-helper="<?php __($file->filename()) ?>" data-text="<?php __($file->dragText()) ?>" href="<?php __($file->url('edit')) ?>">
        <img class="draggable draggable-file customSideThumb" <?php e($file->canHavePreview(), ' data-url="' . $file->crop(75)->url() . '"') ?> data-helper="<?php __($file->filename()) ?>" data-text="<?php __($file->dragText()) ?>" src="<?= $file->crop(75)->url()?>">
        <?php echo $file->filename() ?>

Now, I know I should not directly edit core files, therefore is there a way to extend/modify this snippet outside of the panel folder? I have checked the documentation for creating plugins and creating core components, but it doesn’t seem to document what I need, or I just don’t know that name for what I should be searching for.

Thanks for any help

This would only be possible via a custom form field, in fact, I think there is already such a plugin, I’ll try to find it for you.