Would you consider adding neoadjuvant endocrine therapy in a patient with HR+, HER2- breast cancer who has not clinically responded to neoadjuvant chemotherapy?

Generally no, unless conversion to lumpectomy is a goal. If the patient is not a lumpectomy candidate, then I would move on with surgery. Pathological complete responses are low (10%) in ER+ive cancers, thus it is not unusual to see a modest clinical response with chemotherapy.