There are no official guidelines, except the general rules of tables.
I recommend keeping the print format wherever possible; if the text doesn't fit in a braille table with Spanish text I will key the long pronouns. Since Spanish has abbreviated forms of usted/ustedes, I usually key "el/ella/usted" as "ud" and "ellos/ellas/ustedes" as "uds." (In other texts, the verb charts read "nosotros/nosotras" and "vosotros/vosotras" and may also need to be keyed.)
In terms of the table setup, I prefer to treat these as two columns but still align verbs within each column, adding guide dots where necessary. I would then use an underscore to represent a missing verb. A TN might be helpful to clarify, e.g. "An underscore represents a verb to be filled in." See attached for this example.
An alternative would be to do the chart as four columns, in which case a blank entry would be represented by guide dots across the width of the column. This format lacks a break between singular pronouns/verbs and plural pronouns/verbs, but that probably wouldn't prevent the reader from understanding it.
FYI (not that it really matters) this is a "conjugation" table ("declension" refers to the forms of nouns, adjectives, and pronouns; "conjugation" refers to verb forms)