I’m not sure how it applies to your case, but Obsidian seems to be using the marker thingy to mark the lists, see my post on multi-numbering.
So not sure how, but I do believe you need to change the syntax to be related to the ::marker syntax, to get it to work. But I might be mistaken, I’m not that confident when replying to CSS stuff, it’s still a bit of a grey area for me.