Create one new column of unique data from two columns

create a named range for your first list called "List1" do the same for your second list and call it "List2"

then whereever you want your distinct list of id's to be use the formula below and enter with CSE

=IFERROR(IFERROR(INDEX(list1, MATCH(0, COUNTIF($F$1:F2, list1), 0)), INDEX(list2, MATCH(0, COUNTIF($F$1:F2, list2), 0))), "")