There was an issue with changing the toggle button's position dynamically. The whole markup of the pane was being updated in the client, and it was losing the styling and listeners that had been added when the component was initialized in the client. A fix was applied to detect when there's a change in position of a toggle button in any of the panes that support it and trigger a re-initialization of the component in the client, in order to make sure that all the necessary styling and listeners are applied to the whole panel.
This fix was applied to the 4.3 trunk and to the 4.3 P04 tag.
Added toggleButtonPosition attribute to ace:borderLayoutPane.