TabyP, you should just try the HTML Snippets plug-in.
I’m really ticked I had to resort to it, but my PayPal buttons are now back where they belong.
It allows you to insert shortcode in place of what you need.
I actually linked it in this post, but like everything else WP-related, it doesn’t work.
<a href="https://www.ads-software.com/plugins/insert-html-snippet//"></a>