=IFERROR(MID("!" + JOIN(DISTINCT(COLLECT(List:List, List:List, @cell <> "")), "!") + "!", FIND("|", SUBSTITUTE("!" + JOIN(DISTINCT(COLLECT(List:List, List:List, @cell <> "")), "!") + "!", "!", "|", Number@row)) + 1, FIND("|", SUBSTITUTE("!" + JOIN(DISTINCT(COLLECT(List:List, List:List, @cell <> "")), "!") + "!", "!", "|", Number@row + 1)) - (FIND("|", SUBSTITUTE("!" + JOIN(DISTINCT(COLLECT(List:List, List:List, @cell <> "")), "!") + "!", "!", "|", Number@row)) + 1)), "")
Formula is in [Column2] of the below snippet: