You may use the
AdwordsUserListService.mutateMembers() operation to update an existing audience. All you need to do is to get the
Id of the user list that you want to update using the
AdwordsuserListService.get() and then you may follow this
sample code (also available in other languages) starting from this line "
Long userListId = userListAdded.getId();" (
userListId = YOUR_USERLISTID_TO_BE_UPDATED) to add or remove your email address. You may change the operator (
mutateMembersOperation.setOperator(Operator.ADD);) to ADD or REMOVE based on your preferred operation. Take note that the SET operator is not supported in AdwordsUserListService.mutateMembers().
Let me know if you still need clarifications.