Custom state (e.g. tempo, volume, video related state) should show up in a target that has been 'flattened' via JSON.stringify.

src/sprites/rendered-target.js

@@ -1003,7 +1003,12 @@ class RenderedTarget extends Target {
             variables: this.variables,
             lists: this.lists,
             costumes: costumes,
-            sounds: this.getSounds()
+            sounds: this.getSounds(),
+            tempo: this.tempo,
+            volume: this.volume,
+            videoTransparency: this.videoTransparency,
+            videoState: this.videoState
+
         };
     }