I suggest that when you press Edit, new empty boxes appear (with some hinting at what they are for), where you then use one to name the data and the other to store the data. It would probably look good, if in Edit mode the layout switched to a table.
Additionally, it may be of great UX value to add common "data types" suggestions in that table, for easy population. Things like:
What these common-data-types-for-easy- population are should be possible for the user to change, i.e. also define their own and change the order. This should include whether a field should appear outside of edit mode, like for missing usernames. Obviously, data types the user has created previously should be suggested, when creating a new one.