Update 3 6 action history

3-6-action-history.md

 # Undo & redo (and how to use Actions Pane)
 
+<p align="center">
 ![](img/3-6-actions-pane.png)
 
 The **Actions Pane** displays the history of actions related to the current selected layer.
@@ -9,7 +10,8 @@ You can select an action entry in the action list and
 
 *  Click the *Undo* button or click the *Up* icon to undo the history entry to the former action entry. 
 *  Click the *Redo* button or click the *Down* icon to redo the history entry to the later action entry. 
-   
+ 
+      <p align="center">
       ![](img/3-6-action-control.png)
 
 You can also select an action entry and right-click to select *Undo* or *Redo* options.