Thank you, Cindi. There is no conflict with music code, since the notation is literary. [As a humorous aside, in music context (5)(156) is the quarter note D just above middle C.]
I've practiced using (5)(156) in actual examples, and have found it adds quite a bit of bulk. Examples from exercise material (sequentially lettered items A., B., C. ...), each of the numbers with the "hat" superimposed:
C. Harmonize the soprano melody 5-6-5-4-3 in B minor ...
D. Harmonize the bass melody 1-7-1-2-3-4-5-3 in G minor ...
Because the (5)(156) needs to follow each of the numbers, the scale degree sequence in item D consumes 34 cells.
For a single, isolated scale degree number, 4 cells isn't bad. Sequences of hyphenated scale degrees are fairly common, however, as they indicate a particular sequence of notes.
The (45, 146) says it is a circumflex above the following letter. It seems to me it would also apply to a following number. But that is not what the UEB codebook says. I will check with others and get back to you on this.