toc: add max_level option to limit which heading levels get anchor links

docs/extensions/toc.md

@@ -252,6 +252,12 @@ The following options are provided to configure the output:
     included in the Table of Contents. To exclude this first level, you
     have to set `toc_depth` to `"4-6"`.
 
+* **`link_depth`**
+    Add anchors/permalinks only to headings up to this depth (`h1`–`hN`).
+    Defaults to `6`.
+
+    For example, setting `link_depth` to `2` adds anchors only to `<h1>` and `<h2>` elements.
+
 A trivial example:
 
 ```python

markdown/extensions/toc.py

@@ -257,7 +257,7 @@ def __init__(self, md: Markdown, config: dict[str, Any]):
         self.permalink_class: str = config["permalink_class"]
         self.permalink_title: str = config["permalink_title"]
         self.permalink_leading: bool | None = parseBoolValue(config["permalink_leading"], False)
-        self.header_rgx = re.compile("[Hh][123456]")
+        self.header_rgx = re.compile(f'[Hh][1-{config["link_depth"]}]')
         if isinstance(config["toc_depth"], str) and '-' in config["toc_depth"]:
             self.toc_top, self.toc_bottom = [int(x) for x in config["toc_depth"].split('-')]
         else:
@@ -466,6 +466,12 @@ def __init__(self, **kwargs):
                 'separated by a hyphen in between (`2-5`) defines the top (t) and the bottom (b) (<ht>..<hb>). '
                 'Default: `6` (bottom).'
             ],
+            'link_depth': [
+                6,
+                'Add anchors/permalinks only to headings up to this depth (`h1`–`hN`). '
+                'For example, `link_depth: 2` adds them to `h1` and `h2` only. '
+                'Default: `6`'
+            ]
         }
         """ Default configuration options. """
 

tests/test_syntax/extensions/test_toc.py

@@ -555,6 +555,24 @@ def testAnchorLinkWithDoubleInlineCode(self):
             extensions=[TocExtension(anchorlink=True)]
         )
 
+    def testAnchorLinkWithLinkDepth(self):
+        self.assertMarkdownRenders(
+            self.dedent(
+                '''
+                # Header 1
+
+                ## Header *2*
+                '''
+            ),
+            self.dedent(
+                '''
+                <h1 id="header-1"><a class="toclink" href="#header-1">Header 1</a></h1>
+                <h2>Header <em>2</em></h2>
+                '''
+            ),
+            extensions=[TocExtension(anchorlink=True, link_depth=1)]
+        )
+
     def testPermalink(self):
         self.assertMarkdownRenders(
             '# Header',