multiple-desktops: Add aconfig flag

Flag: EXEMPT adding a flag
Bug: 379158791
Test: Manual
Change-Id: Ia9013af552eb1c8b5e22c60a63e14ad480a97b50
diff --git a/core/java/android/window/flags/lse_desktop_experience.aconfig b/core/java/android/window/flags/lse_desktop_experience.aconfig
index f474b34..eebdeadc 100644
--- a/core/java/android/window/flags/lse_desktop_experience.aconfig
+++ b/core/java/android/window/flags/lse_desktop_experience.aconfig
@@ -402,4 +402,11 @@
     namespace: "lse_desktop_experience"
     description: "Enables HSUM on desktop mode."
     bug: "366397912"
+}
+
+flag {
+    name: "enable_multiple_desktops"
+    namespace: "lse_desktop_experience"
+    description: "Enable multiple desktop sessions for desktop windowing."
+    bug: "379158791"
 }
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