Refactored code to lua modules. Now dialog is object-like table in module. This can make easier to introduce new dialogs with new characters.
Improved visual for dialog. Now player can see which character said by looking on icon of actor at right side of dialog.
Next stage is moving to common place scenario/plot and manage to introduce multilingual one.
With external dialog object it can be as easy as change instance. I presume that language can be changed on fly at any time.
One thing to work with - scenario object to hold dialog/scene objects and divide chapters of visual novell to scenes. It will help debug dialogs fast.