Save our example, compile and run it. Try to add entries to the list in various combinations and merge them. You will see how different access modes behave. Try to combine entries for different users and merge them. You will see that entries for different users does not affect each other. Try to combine various access modes for one or more users. You should be able to observe the access modes behaviour described on previous step. And finally try to press merge button several times. You should see that second and following clicks do not change the ACL.

Well, ACL editor is ready now.