Well, what i though here is:
1. Previous tab stores value via updateValue.
2. If current tab needs paste value in its own editor, it should take current value and put it inside own editor. For example.
   -TinyMCE register its own retrieve value function via retrieveValue method of TabsEditingDescriptorModel in its own template.
  - at line 105 of code, TabsEditingDescriptorModel.retrieveValue is called, if it is not empty.

That is why i left comment, for future changes. I think I can remove it. Or it is better left it there for more easy updates in future. What you think?