docs: playground studio integration (#3514)

docs/docs/cloud/how-tos/iterate_graph_studio.md

@@ -0,0 +1,15 @@
+# Prompt Engineering in LangGraph Studio
+
+In LangGraph Studio you can iterate on the prompts used within your graph by utilizing the LangSmith Playground. To do so:
+
+1. Open an existing thread or create a new one.
+2. Within the thread log, any nodes that have made an LLM call will have a "View LLM Runs" button. Clicking this will open a popover with the LLM runs for that node.
+3. Select the LLM run you want to edit. This will open the LangSmith Playground with the selected LLM run.
+
+![Playground in Studio](../img/studio_playground.png){width=1200}
+
+
+
+From here you can edit the prompt, test different model configurations and re-run just this LLM call without having to re-run the entire graph. When you are happy with your changes, you can copy the updated prompt back into your graph.
+
+For more information on how to use the LangSmith Playground, see the [LangSmith Playground documentation](https://docs.smith.langchain.com/prompt_engineering/how_to_guides#playground).

docs/docs/how-tos/index.md

@@ -290,6 +290,7 @@ LangGraph Studio is a built-in UI for visualizing, testing, and debugging your a
 - [How to test your graph in LangGraph Studio (MacOS only)](../cloud/how-tos/invoke_studio.md)
 - [How to interact with threads in LangGraph Studio](../cloud/how-tos/threads_studio.md)
 - [How to add nodes as dataset examples in LangGraph Studio](../cloud/how-tos/datasets_studio.md)
+- [How to engineer prompts in LangGraph Studio](../cloud/how-tos/iterate_graph_studio.md)
 
 ## Troubleshooting