Docs: update env variables

en/guides/workflow/variables.mdx

@@ -7,11 +7,13 @@ description: Last edited by Allen, Dify Technical Writer
 
 **How to use a fixed symbol to refer dynamically changing content?** Variables, as dynamic data containers, can store and transmit unfixed content, being referenced mutually within different nodes, providing flexible information mobility between nodes.
 
+## Variable Types
+
 ### System Variables
 
 System variables refer to pre-set system-level parameters within Chatflow / Workflow App that can be globally read by other nodes. All system-level variables begin with `sys.`
 
-#### Workflow
+**Workflow**
 
 Workflow type application provides the system variables below:
 
@@ -19,7 +21,7 @@ Workflow type application provides the system variables below:
 
 ![Workflow App System Variables](https://assets-docs.dify.ai/dify-enterprise-mintlify/en/guides/workflow/09d9f977965d41cf056f37a4f8f952db.png)
 
-#### Chatflow
+**Chatflow**
 
 Chatflow type application provides the following system variables:
 
@@ -98,6 +100,8 @@ Environmental variables have the following characteristics:
 * Environment variable names cannot be duplicated;
 * Output variables of nodes are generally read-only and cannot be written to.
 
+![](https://assets-docs.dify.ai/2025/06/8d9342615b3623ef4ce526a583a8de76.png)
+
 ***
 
 ### Conversation Variables
@@ -131,7 +135,7 @@ To track changes in conversation variable values during debugging the applicatio
 
 ![](https://assets-docs.dify.ai/2024/11/cc8067fa4c96436f037f8210ebe3f65c.png)
 
-### Notice
+## Notice
 
 * To avoid variable name duplication, node naming must not be repeated
 * The output variables of nodes are generally fixed variables and cannot be edited