If you don't want to manually fix a lot of things, I think you will at minimum need some formulas. Below is one possible option:
Create delimiters with new formula column
Concat Items(Words(:Letter Sequence, ""), " ")
Then use text to columns with the new delimiter character
jthi_0-1666709951206.png
Stack the data table with the new columns
jthi_1-1666709995611.png
Create new formula column to get the correct Start Letter numbers
Col Min(:Start Letter No., :Letter Sequence) + Col Cumulative Sum(1, :Letter Sequence)
Copy that just created column to other column to get End Letter No (or use formula)
Then you need one more formula, to change first letter's Delta D to 0
If(Row() == Col Min(Row(), :Letter Sequence),
0,
:Delta D
)
Finally cleanup column names to match what you want
jthi_2-1666710269331.png
-Jarmo