Improve History Graph Layout & Dual Axis support and more ?

[penguin-fr]

I’d like to suggest a few possible improvements to the built-in History view and graphs, to make them more flexible and insightful.

🖼️ 1. Dynamic Graph Layout

When only one entity or several with same unit is selected in the History view, the chart currently occupies just a small portion of the screen (about 1/3 height on desktop).
It would be nice to have either:

• A dynamic layout that adjusts the graph height based on the number of entities shown
• And/Or a manual option to resize graph sections for better readability

This would help to have better visibility.

📈 2. Dual Y-Axis Support

Sometimes we need to compare two values with different units (e.g., °C and %, or W and V).
Currently, we can't put them on the same chart.

Adding a second Y-axis on the right (with automatic or manual mapping) would allow meaningful comparisons.

🤔 Not a Priority, But Still Worthwhile

Of course, this is not a priority, especially since we can achieve similar things using external tools like Grafana.
However, I believe that giving the native History view a visual and functional refresh would make Home Assistant feel even more polished out-of-the-box — especially for less technical users or quick insights.

[wrfz]

Basically, I think the suggestion to enlarge the History Panel is a very useful and important feature.
However, in my opinion, it should be designed differently. Explanation:

Vertical Scaling in the History Panel

Depending on the selection in the History Panel (Devices, Areas, or simply multiple Entities), a large number of graphs can be displayed. I believe the suggestion to make the height of all diagrams configurable is not the right approach for the following reasons:

Drawbacks of Global/Automatic Height Scaling

• Excessive Scrolling: A global setting would increase the height of all graphs, regardless of user interest. This forces the user to scroll significantly more to reach a specific graph of interest.

• Low Information Density: Many graphs/entities have almost no information content (e.g., values that display as a continuous horizontal line). It makes no sense to stretch or enlarge these graphs.

• Layout Issues: Scaling the height based on an absolute value or automatically based on the number of entities within the graph is not ideal. For instance, a graph containing 10 entities, all currently at a zero value, would result in a huge, empty diagram, disrupting the layout.

In the History Panel, the user is typically only interested in one or two specific graphs at any given moment.

Proposed Concept: Per-Graph Dynamic Scaling

Each graph in the History Panel receives an overlay button for scaling, similar to the existing Reset button (displayed when user start zooming).

Mechanism

1. Activation: Clicking this button causes the specific graph to scale vertically (with or without animation).

2. Scaling Method: The exact vertical scaling method can be debated, but one option is for the selected graph to occupy the full available height of the viewport/screen.

   • The scroll position could be adjusted ("tweened") so that the top edge of the enlarged graph aligns with the top of the viewport.

3. Deactivation: Clicking the button again reverts the graph's height back to its original size.

Alternative Options

It would also be conceivable to use two buttons (Enlarge + Shrink) that could be pressed repeatedly to increase or decrease the size in steps.

However, my personal preference is the single toggle button approach (Enlarge to Full View / Return to Default).

[wrfz]

@penguin-fr It would be great if you could create a separate discussion thread for your second suggestion, Dual Y-Axis Support and move it there. Just to avoid confusion caused by two different topics in one thread.