unluckily, when dealing with numbering, this is always a pain. It's terribly bad designed.
I used this
The 2nd underlying level doesn't work. Why? This is due to my laziness : to avoid creating a new NumberDefinition each time I encounter <ol>/<ul>, I try to reuse an existing one.
Instead, MS Word will create a whole new definition with MultiLevel ad-hoc. Your sample is "easy" but what when people want to mix different list:
I think, I have to start a new whole definition too and don't care if there are many list definition in the documents.
I used this
<olstyle="list-style-type: upper-alpha"><li>This is H1 <olstyle="list-style-type: decimal"><li>This is H2</li><li>Another H2</li></ol></li><li>This is another H1 <olstyle="list-style-type: decimal"><li>This is H2</li><li>Another H2</li></ol></li><li>Last H1 <olstyle="list-style-type: decimal"><li>This is H2</li><li>Another H2</li></ol></li></ol>
Instead, MS Word will create a whole new definition with MultiLevel ad-hoc. Your sample is "easy" but what when people want to mix different list:
1.
i.
ii.
2.
a.
b.