Hello,
Thank you for contacting Rank Math and bringing your concern to our attention.
It seems that you wanted to add a toggle button in the TOC block of Rank Math.
In this case, you can follow the steps provided by my colleague in this similar ticket to achieve that on your site.
Hope that helps.
Thank you.
I have followed that tutorial and added php code on my child theme functions.php file.
But it can work only in administrative login, without site login it won’t work.
and browser console is showing the error:

Hello,
Can you please confirm if the CSS styling is only loaded upon admin login?
As for the JS error, you would need to enqueue the jQuery library first as it seems that your theme doesn’t support it.
You may add this code:
add_action('wp_enqueue_scripts', 'my_register_script_method');
function my_register_script_method () {
wp_register_script( 'jqueryexample', 'http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jqueryexample.min.js');
}
If you prefer, we can take a closer look at the issue. Please edit the first post on this ticket and include your WordPress & FTP logins in the designated Sensitive Data section.
Please do take a complete backup of your website before sharing the information with us.

It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
We really look forward to helping you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.