Switching out the list-style-type doesn't seem to do anything for a ul li ul li. Not sure if it's possible.
https://jsfiddle.net/swfkmo9t/
<ul>
<li>
<ul>
<li>this is a test</li>
</ul>
</li>
</ul>
ul li ul li::marker{
list-style-type: square;
}