Issue in detail:
Let say we have 4 major tasks: A, B, C, D such that following combinations are considered valid:
1) A->B->C->D
2) A->C->D
3) A->B->C
4) A->D
 and so on.

On top of that, we would like to allow users to customize the flow of tasks as following:
1) A->myOperations->D
2) A->preTaskDoperations->D->postTaskDoperations.


Currently, I have support for user flow without this customization like 
1) A->B->C->D
2) A->C->D
3) A->B->C
4) A->D
 and so on.
Note: same was mentioned above earlier.