I know little about Phppgadmin, but I think that you can't do that - customize the order in which the columns are displayed- it's determined by the DB schema.
And, even if you wanted to do that in the underlying db, it would be not easy, Postgresql does not support column reordering: you would need to dump-edit-restore the table, or do a SELECT ... INTO ... followed by a RENAME and DROP TABLE; but you would need to fix manually dependecies in this case (views, FK, sequences, etc).
It's true that the column order in a database has little relevance from the pure relational point of view, but in practical use it's nice to have related fields together, it helps when browsing.
One alternative (probably unsastifactory) is to define a VIEW which mirrors a table, with the columns reordered, and use that for browsing. It would not be useful for updating, though... among other shortcomings.