I wrote the Etherpad Ordered List implementation. it would be easy to do what you want with CSS.
Place the followin in your src/static/custom/pad.css
/* The behavior for incrementing and the prefix */
.list-number1 li:before {
content: "§" counter(first);
counter-increment: first;
}
.list-number2 li:before {
content: counter(first) ")";
counter-increment: second;
}
.list-number3 li:before {
content: counter(first) ".";
counter-increment: third 1;
}
Ensure when you refresh your page that it hasn't loaded the minified/cached version of custom/pad.css
I find it bizarre that this got down-voted.. OP can you please confirm this is the correct answer?
Again it's worth noting I wrote the implementation in Etherpad Core so I'm kinda familiar with this...