docs: document using conditional operators in workflows (#9464)

www/apps/book/app/advanced-development/workflows/constructor-constraints/page.mdx

@@ -114,6 +114,44 @@ const myWorkflow = createWorkflow(
 })
 ```
 
+### No Conditional Operators
+
+You can't use conditional operators in a workflow, such as `??` or `||`.
+
+<Note>
+
+Learn more about why you can't use if-conditions [in this chapter](../conditions/page.mdx#why-if-conditions-arent-allowed-in-workflows)
+
+</Note>
+
+Instead, use `transform` to store the desired value in a variable.
+
+For example:
+
+```ts
+// Don't
+const myWorkflow = createWorkflow(
+  "hello-world", 
+  function (input: WorkflowInput) {
+    const message = input.message || "Hello"
+})
+
+// Do
+// other imports...
+import { transform } from "@medusajs/framework/workflows-sdk"
+
+const myWorkflow = createWorkflow(
+  "hello-world", 
+  function (input: WorkflowInput) {
+    const message = transform(
+      {
+        input
+      },
+      (data) => data.input.message || "hello"
+    )
+})
+```
+
 ---
 
 ## Step Constraints