Missed HSN Summary in GSTR 1

A user who exports software services and is below the GST threshold realised they missed adding the HSN summary in their GSTR 1 filing. They are seeking advice on whether this is mandatory for exports, if it can be added later, or what alternative steps they can take. The consensus suggests that for export of services to B2B customers outside India, HSN summary might not be strictly required, but clarification is sought on rectifying the omission.