nvim-treesitter/queries/markdown/highlights.scm

;From MDeiml/tree-sitter-markdown & Helix
(setext_heading (paragraph) @text.title.1 (setext_h1_underline) @text.title.1.marker)
(setext_heading (paragraph) @text.title.2 (setext_h2_underline) @text.title.2.marker)

(atx_heading (atx_h1_marker) @text.title.1.marker (inline) @text.title.1)
(atx_heading (atx_h2_marker) @text.title.2.marker (inline) @text.title.2)
(atx_heading (atx_h3_marker) @text.title.3.marker (inline) @text.title.3)
(atx_heading (atx_h4_marker) @text.title.4.marker (inline) @text.title.4)
(atx_heading (atx_h5_marker) @text.title.5.marker (inline) @text.title.5)
(atx_heading (atx_h6_marker) @text.title.6.marker (inline) @text.title.6)

[
  (link_title)
  (indented_code_block)
  (fenced_code_block)
] @text.literal

(info_string) @label

(pipe_table_header (pipe_table_cell) @text.title)

(pipe_table_header "|" @punctuation.special)
(pipe_table_row "|" @punctuation.special)
(pipe_table_delimiter_row "|" @punctuation.special)
(pipe_table_delimiter_cell) @punctuation.special

[
  (fenced_code_block_delimiter)
] @punctuation.delimiter

(code_fence_content) @none

[
  (link_destination)
] @text.uri

[
  (link_label)
] @text.reference

[
  (list_marker_plus)
  (list_marker_minus)
  (list_marker_star)
  (list_marker_dot)
  (list_marker_parenthesis)
  (thematic_break)
] @punctuation.special


(task_list_marker_unchecked) @text.todo.unchecked
(task_list_marker_checked) @text.todo.checked

(block_quote) @text.quote

[
  (block_continuation)
  (block_quote_marker)
] @punctuation.special

[
  (backslash_escape)
] @string.escape

(inline) @spell