How to create a sticky ToC?

[Tim]

I am using the Three column section with sidebars. On the left sidebar, I have a custom Div in which I put a ToC and a children display macro. 

Also, I created a custom stylesheet with following styles:

.toc-btf { 
 position: -webkit-sticky;
 position: sticky;
 top: 200px;
}

I gave the div the classname but the code didn't work. 

I tried using position: fixed and it worked. But since I am creating a template, I can't use this workaround since using the fixed attribute, the page becomes vulnerable to breaking the layout. Because of that, I am searching ofr a way to make sticky work.

I can't use custom HTML since there is no macro and I can't get one.