Hello,
Thank you for your query and we are so sorry about the trouble this must have caused.
Please try this CSS code to adjust the spacing:
#rank-math-toc ul li > ul{
margin-top: 10px;
}
Here’s a guide you can follow to add this custom CSS on your site:
https://www.wpbeginner.com/plugins/how-to-easily-add-custom-css-to-your-wordpress-site/
Hope that helps and please do not hesitate to let us know if you need my assistance with anything else.
Whenever I made some changes in the HTML code through Edit as HTML, the block got corrupted
Hello,
Our TOC block is not meant to be edited using HTML.
To adjust the line height, head over to Table of Contents Block Settings > Typography > Tools > Line height

Then, adjust the line height to your preferred settings.

Hope that helps and please do not hesitate to let us know if you need my assistance with anything else.
There is no Line height option in my settings
Hello,
The availability of the style option in our table of contents block will depend on your WordPress theme.
If you’re not able to find the Line Height option, it means that the theme you are currently using doesn’t include support for this feature from the WordPress guidelines:
https://developer.wordpress.org/block-editor/how-to-guides/themes/theme-support/#spacing-control
In this case, you may need to get in touch with your theme provider to update their code and include support for that.
Looking forward to helping you.
Thank 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.