Update model comparison page (#1036)

docs/webapp/webapp_model_comparing.md

@@ -23,8 +23,10 @@ it from the comparison.
 You can add/remove models to your comparison:
 1. Click the `+` button in any of the comparison tabs. This opens up a window with a model table with the currently 
 compared models at the top.
+
    ![Adding models](../img/webapp_compare_model_select_2.png#light-mode-only)
-![Adding models](../img/webapp_compare_model_select_2_dark.png#dark-mode-only)
+   ![Adding models](../img/webapp_compare_model_select_2_dark.png#dark-mode-only)
+
 1. Find the models to add by sorting and [filtering](webapp_model_table.md#filtering-columns) the models with the 
 appropriate column header controls. Alternatively, use the search bar to find models by name.
 1. Select models to include in the comparison (and/or clear the selection of any models you wish to remove).
@@ -57,7 +59,7 @@ information is displayed in a column, so each field is lined up side-by-side.
 
 The model on the left is used as the base model, to which the other models are compared. You can set a new base model 
 in one of the following ways:
-* Hover and click <img src="/docs/latest/icons/ico-arrow-from-right.svg" alt="Switch base task" className="icon size-md space-sm" /> 
+* Hover and click <img src="/docs/latest/icons/ico-arrow-from-right.svg" alt="Switch base model" className="icon size-md space-sm" /> 
 on the model that will be the new base.
 * Hover and click <img src="/docs/latest/icons/ico-drag.svg" alt="Pan icon" className="icon size-md space-sm" /> on the new base model and drag it all the way to the left
 
@@ -82,16 +84,25 @@ Switch on the **Show row extremes** toggle to highlight each variant's maximum a
 ![side-by-side scalar comparison](../img/webapp_compare_models_scalar_table_dark.png#dark-mode-only)
 
 
-### Graphic Comparison
-The **Scalars** (Graph view) and **Plots** tabs display plots attached to the models. The **Scalars** tab compares 
-scalar values as time series line charts. The **Plots** tab compares the last reported iteration sample of each 
-metric/variant combination per compared model. 
+### Plot Comparison
+The **Scalars** (Graph view) and **Plots** tabs display plots attached to the models. 
 
-Line, scatter, box, and bar graphs are compared by a single plot per metric/variant into which the plots of all compared 
-models are combined.
+The **Scalars** tab compares scalar values as time series line charts. The **Plots** tab compares the last reported 
+iteration sample of each metric/variant combination per compared model.
 
-![Merged plots](../img/webapp_compare_models_merge_plots.png#light-mode-only)
-![Merged plots](../img/webapp_compare_models_merge_plots_dark.png#dark-mode-only)
+Line, scatter, box, and bar graphs are compared by overlaying each metric/variant from all compared models' into a single 
+comparative plot.
+
+For overlaid plots, use **Group by** to select how to group plots:
+* **Metric** - All variants for a metric appear on the same plot.
+
+   ![Scalar plot grouped by metric](../img/webapp_compare_models_merge_plots.png#light-mode-only)
+   ![Scalar plot grouped by metric](../img/webapp_compare_models_merge_plots_dark.png#dark-mode-only)
+
+* **Metric+Variant** (default) - Every variant appears on its own plot.
+
+   ![Scalar plot grouped by metric and variant](../img/webapp_compare_models_variant_plots.png#light-mode-only)
+   ![Scalar plot grouped by metric and variant](../img/webapp_compare_models_variant_plots_dark.png#dark-mode-only)
 
 Other plot types are displayed separately for each model.