Converting 2 column tally into single column

Hi RichFrench 

Another 365 LAMBDA option:

=XLOOKUP(
    SEQUENCE(SUM(Frequency)),
    SCAN(,Frequency, LAMBDA(acc,v, acc+v)),
    Subject,
    ,1
)

If Excel 2021 (LAMBDA not avail.):

=XLOOKUP(
    SEQUENCE(SUM(Frequency)),
    SUBTOTAL(9,OFFSET(Frequency,,,SEQUENCE(ROWS(Frequency)))),
    Subject,
    ,1
)

RichFrench 

If you're on 365 you might use a LAMBDA.

Please see attached workbook.

RichFrench 

Maybe with Power Query like in the attached file.