Definitely feasible to do with my Lister stack. 
You will want to set the List Point Style to Decimal in the stack settings.
Set the Content Type to HTML Code. Regretfully HTML code is about the only reliable way towards accomplishing a nested list in RapidWeaver nowadays.
Within the stack content area, markup your new list as an ordered (numbered) list, like this:
<ol>
<li>Feed cat
<ol>
<li>Rinse bowl</li>
<li>Open cat food</li>
<li>Mix dry and wet food in bowl</li>
<li>Deliver on a silver platter to Pixel</li>
</ol>
</li>
<li>Wash car
<ol>
<li>Vacuum interior</li>
<li>Wash exterior</li>
<li>Wax exterior</li>
</ol>
</li>
<li>Grocery shopping
<ol>
<li>Plan meals</li>
<li>Clean out fridge</li>
<li>Make list</li>
<li>Go to store</li>
</ol>
</li>
</ol>
Your Lister stack settings will look like this:
Then all that remains is to add this custom CSS code to the RapidWeaver Page Inspector:
.listerWrapper ol {
counter-reset: item;
}
.listerWrapper li {
display: block;
}
.listerWrapper li:before {
content: counters(item, ".") ".";
counter-increment: item;
float: left;
margin-right: 5px;
}
.listerWrapper li li:before {
content: counters(item, ".") " ";
counter-increment: item;
}
This CSS extends our default decimal / ordered list styling through means of the CSS content property. It uses a counter increment to fetch the number of the parent and merge that with the current list item index and include the decimal point(s). It also correctly floats the new list numbers, to ensure they correctly line up.
The CSS above is widely supported by all web browsers as far back as IE8, even though you may have never seen counter or counter-increment properties before. This would be a reliable technique to use in RapidWeaver.
You should finish with something that looks like this:
The screenshot above is from within my Blank theme - things may look different in other themes.
Your existing spacing and indentation settings in the stack should still function, should you need to adjust any of these.
