Org Mode plain lists uses the hyphen (minus sign) character as it’s default bullet. The hyphen is pretty wimpy compared to the Asterisk character so it can be hard to read. Here is some code to visualize it with an Em-Dash instead—so much easier to read!
(font-lock-add-keywords 'org-mode '(("^[[:space:]]*\\(-\\) " 0 (prog1 () (compose-region (match-beginning 1) (match-end 1) "—")))))
Hyphen on the left and em-dash on the right
You can use that code for any character not just em-dash