How to merge two lists

Try this in B14, fill down and across.

Formula:

=IFERROR(1/(1/SUMIFS(INDEX($A$2:$E$9,,MATCH(B$13,$A$1:$E$1,0)),INDEX($A$2:$E$9,,MATCH(B$13,$A$1:$E$1,0)-1),$A14)),"")

Unfortunately this is all I have been able to come up with for the unique Products. Array enter this in A14 and fill down until you get blanks. If you aren’t familiar with array-entered formulas array enter means the formula must be committed from edit mode by simultaneously pressing and holding down Ctrl and Shift while hitting Enter.

Formula:

=IFERROR(INDEX(T(INDIRECT(TEXT(MODE.MULT(IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9)),

IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9))),"R0C00000"),FALSE)),

SMALL(IF(MATCH(T(INDIRECT(TEXT(MODE.MULT(IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9)),

IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9))),"R0C00000"),FALSE)),

T(INDIRECT(TEXT(MODE.MULT(IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9)),

IF(ISTEXT($A$2:$E$9),10^5*ROW($A$2:$E$9)+COLUMN($A$2:$E$9))),"R0C00000"),FALSE)),0)=

ROW(INDIRECT("1:"&ROWS($A$2:$E$9)*2)),ROW(INDIRECT("1:"&ROWS($A$2:$E$9)*2))),ROWS(A$14:A14))),"")

You could do this easily with Power Query (Get & Transform). Let me know if you would like to know how.