What's the next logical step for this Kakuro?

Question

The puzzle is small but frustrating.

Here's what I've deduced so far:

• In the 36 row, there are two missing digits which sum to 9, these must be 1+8 so the remaining empty cells are 2,3,4
• In the 36 column, same thing but it could be 3+6 or 4+5 missing. There must be 1 and 2 somewhere but can't nail down where
• In the 18 row, the leftmost cell is 5 or 6, so the other two sum to 5 or 6, unfortunately that still leaves lots of possibilities
• In the 19 column, there are 4 cells which sum to 10 so must be 1+2+3+4

Alternatively maybe I just overlooked something really stupid.

I have verified all pen (blue) numbers are correct using the button in the app.

Source: Puzzle Page app

Answer 1

Start with the horizontal 18 sum at the bottom.

The cell next to the 7 cannot contain a 5, because that would force the first cell to be 6 and then the final cell would make the sum exceed 18.

From that you know that in the vertical sum

of 36, the top empty cell must be the 6, because otherwise the empty cells would add up to just 10, which is not enough to make 36.