Update legend.md

Author: LiamConnors

doc/python/legend.md

@@ -6,7 +6,7 @@ jupyter:
       extension: .md
       format_name: markdown
       format_version: '1.3'
-      jupytext_version: 1.17.2
+      jupytext_version: 1.19.1
   kernelspec:
     display_name: Python 3 (ipykernel)
     language: python
@@ -20,7 +20,7 @@ jupyter:
     name: python
     nbconvert_exporter: python
     pygments_lexer: ipython3
-    version: 3.9.0
+    version: 3.14.3
   plotly:
     description: How to configure and style the legend in Plotly with Python.
     display_as: file_settings
@@ -832,6 +832,63 @@ fig.show()
 
 ```
 
+### Legend Title Click Behavior
+
+*New in 6.6*
+
+When a figure has multiple legends:
+
+- Single-clicking a legend title toggles the visibility of all items in that legend
+- Double-clicking a legend title toggles the visibility of all items in other legends
+
+This default behavior can be changed for a legend by setting `titleclick` and `titledoubleclick`, which accept:
+- `"toggle"`: toggles the visibility of items in the clicked legend
+- `"toggleothers"`: toggles the visibility of items in other legends
+- `False`: disables click behavior
+
+For example, to swap the behaviors:
+
+```python
+import plotly.graph_objects as go
+
+fig = go.Figure(
+    data=[
+        go.Scatter(x=[1, 2, 3], y=[1, 2, 3], name="Trace 1"),
+        go.Scatter(x=[1, 2, 3], y=[2, 3, 4], name="Trace 2"),
+        go.Scatter(x=[1, 2, 3], y=[3, 4, 5], name="Trace 3", legend="legend2"),
+        go.Scatter(x=[1, 2, 3], y=[4, 5, 6], name="Trace 4", legend="legend2"),
+    ],
+    layout=dict(
+        legend=dict(
+            title=dict(text="First Legend"),
+            titleclick="toggleothers",
+            titledoubleclick="toggle",
+        ),
+        legend2=dict(
+            title=dict(text="Second Legend"),
+            titleclick="toggleothers",
+            titledoubleclick="toggle",
+            y=0.5,
+        ),
+    ),
+)
+
+fig.show()
+```
+
+<!-- #region -->
+To disable title click behavior, set `titleclick` and `titledoubleclick` to `False`:
+
+```python
+fig.update_layout(
+    legend=dict(titleclick=False, titledoubleclick=False),
+    legend2=dict(titleclick=False, titledoubleclick=False),
+)
+```
+
+> **Note:** Legend title click interactions are not supported for legends containing pie or pie-like traces.
+<!-- #endregion -->
+
 #### Reference
 
 See https://plotly.com/python/reference/layout/#layout-legend for more information!