Hi there,

Thanks for those informations. In order for you to achieve this. You will need to do some customizations on your current blog post. You can refer here https://www.tipsandtricks-hq.com/simple-table-of-contents-toc-using-pure-html-and-css-code-9217 on how to achieve this.

To apply those codes, you will need to change your editor to TinyMCE(Easier way to implement codes) or using HTML blocks for built in editor. For example, you can refer screenshot below.

TinyMCE
By clicking 'Toggle Editor' you will see codes for your blog contents as you can see here https://take.ms/XjaSk

Built-in editor(HTML blocks)
Insert HTML blocks https://take.ms/SkSQt and include those codes accordingly as you can see here https://take.ms/GjuYh

You can refer codes on attached files below.

Note:
If you change your editor, it will only affect new articles and previous articles will retain previous used editor.