it can be generated through apps script and you can access/retrieve/modify each item...
Here is a custom numbered list with a prefix:
Prefix 1. item1
Prefix 2. item2
Prefix 3. item3
I didn't find how to generate such a list with apps script, though it is possible through script to insert additional items based on the LIST_ID if the list was manually started through google docs UI.
Apart from creating such a list from scratch, I would also like to be able to loop through all ListItems in a document and retrieve the "Prefix" to compare with some predefined text.
I have the feeling that this is some kind of unsupported element but I would like to confirm this.
Regards