docs: update anywidget_mode notebook with multi-column sorting instructions

Author: shuoweil

notebooks/dataframes/anywidget_mode.ipynb

@@ -50,7 +50,7 @@
     "**Key features:**\n",
     "- **Rich DataFrames & Series:** Both DataFrames and Series are displayed as interactive widgets.\n",
     "- **Pagination:** Navigate through large datasets page by page without overwhelming the output.\n",
-    "- **Column Sorting:** Click column headers to toggle between ascending, descending, and unsorted views.\n",
+    "- **Column Sorting:** Click column headers to toggle between ascending, descending, and unsorted views. Use **Shift + Click** to sort by multiple columns.",
     "- **Column Resizing:** Drag the dividers between column headers to adjust their width."
    ]
   },
@@ -489,13 +489,20 @@
    "id": "sorting-intro",
    "metadata": {},
    "source": [
-    "### Sorting by Single-Column\n",
+    "### Sorting by Column(s)\n",
     "You can sort the table by clicking on the headers of columns that have orderable data types (like numbers, strings, and dates). Non-orderable columns (like arrays or structs) do not have sorting controls.\n",
     "\n",
-    "**Sorting indicators (▲, ▼) are always visible for sorted columns. The unsorted indicator (●) is only visible when you hover over an unsorted column header.** The sorting control cycles through three states:\n",
+    "#### Single-Column Sorting\n",
+    "The sorting control cycles through three states:\n",
     "- **Unsorted (no indicator by default, ● on hover):** The default state. Click the header to sort in ascending order.\n",
     "- **Ascending (▲):** The data is sorted from smallest to largest. Click again to sort in descending order.\n",
-    "- **Descending (▼):** The data is sorted from largest to smallest. Click again to return to the unsorted state."
+    "- **Descending (▼):** The data is sorted from largest to smallest. Click again to return to the unsorted state.\n",
+    "\n",
+    "#### Multi-Column Sorting\n",
+    "You can sort by multiple columns to further refine your view:\n",
+    "- **Shift + Click:** Hold the `Shift` key while clicking additional column headers to add them to the sort order. \n",
+    "- Each column in a multi-sort also cycles through the three states (Ascending, Descending, Unsorted).\n",
+    "- **Indicator visibility:** Sorting indicators (▲, ▼) are always visible for all columns currently included in the sort. The unsorted indicator (●) is only visible when you hover over an unsorted column header."
    ]
   },
   {