=ARRAYFORMULA(QUERY(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IF(A:B<>"", A:B&"♦", ))
,,999^99)),,999^99), "♦")), "where Col1 is not null"))

=ARRAYFORMULA(QUERY(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(
IF(A:B<>"", A:B&"♦ ♦", )),,999^99)),,999^99), "♦")), "limit "&COUNTA(A:B)*2-1))
