This app does EVERYTHING I need (and then some !), that the built-in app doesnt do (or doesnt do easily or intuitively). If you include the same developers Copy/Merge app, you can do anything pertaining to your contacts (as I found out in the case mentioned below).
Thank You Very Much and
Well Done !!!
The one "gotcha" case that I just figured out (I didnt contact their support, which I could have, but I like to figure out my own mistakes ;-) is that if you try to add a contact to a group, both have to be in the same account. Otherwise, when you try to add the contact to a group, you dont see any of your groups, as theyre in a different account (a limitation by how Apple stores your contacts).
This, obviously being a "user error", was fixable by moving the contact to my main account (which contains all my groups), all being done using the developers two main apps ("Contacts A to Z" and "Contacts Sync/Move"). And, for those interested, I traced the source of this problem to my "default contact add" setting.
Have-Used-App about A2Z Contacts - Group Text App