Adding documentation on example workflows customization.

custom-nodes/workflow_templates.mdx

@@ -28,6 +28,49 @@ Under `ComfyUI-MyCustomNodeModule/example_workflows/` directory:
  - `My_example_workflow_1.jpg`
  - `My_example_workflow_2.json`
 
-In this example ComfyUI's template browser shows a category called `ComfyUI-MyCustomNodeModule` with two items, one of which has a thumbnail.
-
+In this example ComfyUI's template browser shows a category called `ComfyUI-MyCustomNodeModule` with two items, one of which has a thumbnail.
+
 For a real-world example, see [ComfyUI-Impact-Pack's example_workflows folder](https://github.com/ltdrdata/ComfyUI-Impact-Pack/tree/Main/example_workflows).
+
+## Customization
+More extensive configuration can be done by adding an `index.json` to the example workflow folder.
+This index should follow the core workflows standard and optionaly contain:
+* `description` the custom node description
+* `templates` A list of The customized templates
+
+Each template can contain the following keys:
+* `name`: needs to match the template file name. Mandatory
+* `title`: The template title. Optional, default to workflow name
+* `description`: The title description. Optional, default to workflow name
+* `mediaSubtype`: the workflow thumbnail file(s) extenstion (`jpg`, `png`, `webp`, ...), default to `jpg`. Optional.
+* `thumbnailVariant`: custom thumbnail variant, either `compareSlider` or `hoverDissolve` for now. Requires a `mediaSubtype` to be set and the thumbnails files suffixed with `-1` and `-2`. Optional
+
+### Example
+This example `index.json`
+```json
+{
+  "description": "An awesome CustomNode module.",
+  "templates": [
+    {
+      "name": "My_example_workflow_1",
+      "title": "My First Workflow",
+      "description": "A workflow generating an awesome Image.",
+    },
+    {
+      "name": "My_example_workflow_2",
+      "title": "My Second Workflow",
+      "description": "A workflow upscaling an image with more details.",
+      "mediaSubtype": "webp",
+      "thumbnailVariant": "compareSlider"
+    }
+  ]
+}
+```
+
+Will work with the following structure under `ComfyUI-MyCustomNodeModule/example_workflows/` directory:
+ - `index.json`
+ - `My_example_workflow_1.json`
+ - `My_example_workflow_1.jpg`
+ - `My_example_workflow_2.json`
+ - `My_example_workflow_2-1.webp`
+ - `My_example_workflow_2-2.webp`