If you break, indent parameters under the call

DATA(sum) = add_two_numbers(
                value_1 = 5
                value_2 = 6 ).

Aligning the parameters elsewhere makes it hard to spot what they belong to:

" anti-pattern
DATA(sum) = add_two_numbers(
    value_1 = 5
    value_2 = 6 ).

However, this is the best pattern if you want to avoid the formatting to be broken by a name length change.