`groupclick="toggleitem"` Does Not Work Consistently Across Subplots in Plotly

Description

When using the groupclick="toggleitem" parameter in Plotly with subplots, the toggling behavior for legend items only applies to traces in the first subplot. Traces in other subplots are not affected as expected, even when the legendgroup attribute is set consistently for all relevant traces.

This issue breaks the intended behavior of groupclick="toggleitem" for figures with subplots, where users would expect the toggling of a legend item to apply uniformly across all traces in the same legendgroup, regardless of their subplot.

Expected Behavior

Clicking a legend item with groupclick="toggleitem" should toggle the visibility of all traces in the corresponding legendgroup, including traces in subplots other than the first.

Observed Behavior

When clicking a legend item:

• The visibility of traces is toggled only in the first subplot.

• Traces in other subplots within the same legendgroup remain unaffected.

Minimal Reproducible Example

import plotly.graph_objects as go
from plotly.subplots import make_subplots

# Create a subplot figure
fig = make_subplots(rows=3, cols=1)

# Add traces to the first subplot
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[1, 4, 9], name="Group A", legendgroup="group_a"), row=1, col=1)
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[2, 4, 8], name="Group B", legendgroup="group_b"), row=1, col=1)

# Add traces to the second subplot
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[1, 3, 6], name="Group A", legendgroup="group_a", showlegend=False), row=2, col=1)
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[2, 5, 7], name="Group B", legendgroup="group_b", showlegend=False), row=2, col=1)

# Add traces to the third subplot
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[1, 2, 3], name="Group A", legendgroup="group_a", showlegend=False), row=3, col=1)
fig.add_trace(go.Scatter(x=[1, 2, 3], y=[3, 5, 9], name="Group B", legendgroup="group_b", showlegend=False), row=3, col=1)

# Update layout with groupclick parameter
fig.update_layout(
    legend=dict(groupclick="toggleitem")
)

fig.show()

Steps to Reproduce

1. Run the provided example code.

2. Click on a legend item for "Group A" or "Group B."

3. Observe that the traces in the first subplot toggle visibility as expected.

4. Notice that traces in other subplots do not toggle visibility.

### Environment

Plotly Version: 5.24.1
Python Version: 3.11.9
Operating System: Windows 11
Browser: Edge 131.0.2903.86

Additional Notes

The issue does not occur when the groupclick parameter is omitted. The default behavior works as expected, where clicking a legend item toggles all traces in the same legendgroup across all subplots.

However, groupclick="toggleitem" is necessary for more granular control of legend interactions, and it should work consistently across subplots.

Start by running the provided Python minimal reproducible example with Plotly 5.24.1 and verify the legend behavior across all three subplots. Trace the legend interaction entry point in the repository or its Plotly.js integration, then add coverage for groupclick="toggleitem" with shared legend groups. Done means clicking a legend item consistently applies the expected visibility change across every subplot.