To obtain a new Search Tree view at restart, type:

while(debugger.initialize()) { 
      solver.startNewSearch(myGoal); 
      if (solver.next()) { 
         ostrstream text; 
         text << solver.getValue(makespan)<< endl << ends; 
         debugger.sendSolution(text.str()); 
         debugger.newSearchTreeView(); 
         solver.restartSearch(); 
         if (solver.next()) { 
            ostrstream text; 
            text << solver.getValue(makespan)<< endl << ends; 
            debugger.sendSolution(text.str()); 
        } 
      } 
      solver.endSearch(); 
} 

You can also choose to reuse the same Search Tree view. In that case, the root node will have four branches.