You can use - or + to create bullet points: is there a way to change how just ONE looks?

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I don’t think Obsidian’s underlying markup notes which list marker was used, so you’ll probably need another way to mark your lists. One option would be to put them in custom callouts.

Also, in Markdown when you change the list marker type it starts a new list. So this is 1 list:

- one
- two
  • one
  • two

And this is 2 (very short) lists:

- one
+ two
  • one
  • two

You can see that the rendered versions here have different spacing because of that.