USCIS announced updates to its guidance on discretion in immigration decisions on July 15, 2020. While this guidance is aimed at adjudicators who are deciding whether to approve a benefit, it should be useful for arguing positive discretionary factors as well. The updates can be found in the USCIS Policy Manual:

https://www.uscis.gov/policy-manual/volume-1-part-e-chapter-8

https://www.uscis.gov/policy-manual/volume-10-part-a-chapter-5