That's quite a practical question. When using only UEB (and no Nemeth), what do we do with single-digit addition problems arranged spatially for calculation?
I would do exactly as you have done, beginning the summation line one cell to the right of the plus sign with those one-digit numbers starting one more cell to the right so that the column above the dot 5 of the horizontal line is empty.
Unrelatedly, please let me suggest that you use a consistent number of cells between the rightmost part of one column of spatial problems and the identifier of a problem placed to the left. (In your example, I think there are two blank cells between the first and second problems but three blank cells between the second and third problems on each line.)
Thank you for your diligent questions and clear examples. Braille on!