IncrementLastNumber.excel.lambda.txt

=LAMBDA(
  LET(
    upRange, INDIRECT(ADDRESS(1, COLUMN()) & ":" & ADDRESS(ROW() - 1, COLUMN())),
    lastNumber, LOOKUP(2, 1 / ISNUMBER(upRange), upRange),
    IF(ISNUMBER(lastNumber),
      lastNumber + 1,
      ""
    )
  )
)

SubtotalLeft.excel.lambda.txt

=LAMBDA(
  LET(
    upRange, INDIRECT(ADDRESS(1, COLUMN()) & ":" & ADDRESS(ROW() - 1, COLUMN())),
    lastNonBlankRow, LOOKUP(2, 1 / (ISBLANK(upRange) = FALSE), ROW(upRange)),
    IF(ISNUMBER(lastNonBlankRow),
      SUM(INDIRECT(ADDRESS(lastNonBlankRow + 1, COLUMN() - 1) & ":" & ADDRESS(ROW(), COLUMN() - 1))),
      SUM(INDIRECT(ADDRESS(1, COLUMN() - 1) & ":" & ADDRESS(ROW(), COLUMN() - 1)))
    )
  )
)