Aria Attributes

I am currently trying to make our website compliant with WCAG 2.1 guidelines. At present the “Contents [show/hide]” does not have any Aria attributes and as such flagged as a fail.

Is it possible to edit the TOC+ plugin php so that the following rendered html:-

<span class="toc_toggle">[<a href="#">hide</a>]</span>

would become –

<span class="toc_toggle">[<a href="#" aria-haspopup="true" aria-expanded="true" 
>hide</a>]</span>

and

<span class="toc_toggle">[<a href="#">show</a>]</span>

would become –

<span class="toc_toggle">[<a href="#" aria-haspopup="true" aria-expanded="false" 
>hide</a>]</span>

Thanks in advance for any help offered on this.

The page I need help with: [log in to see the link]