The basic guideline that a code should be assigned for conditions "that require or affect patient care, treatment or management" applies to facility coding as it would to any other place of service. The main difference is that in a short office encounter, the physician note usually encompasses of all the relevant information since the physician's assessment and plan usually documents the whole purposes of the visit, whereas in a facility the treatment involves the full staff under supervision of physicians who will often give orders to continue home medications, treatments, diets, etc. for the chronic conditions. So in facility coding, it may be necessary, or possible, to pull conditions from history or problems lists to match with those medications and treatments that are administered during the outpatient encounter. It should be mentioned, though, that nursing notes may not be used to assign codes, with the exception of the small number of situations listed in the guidelines (e.g. depth of pressure ulcers, SDOH, etc.) where codes are allowed to be assigned from documentation by non-physician clinical staff. Otherwise, only documentation authored by physicians and NPPs can be used for code assignment.
But really, I think your hospital leadership really should be giving you guidance on this as to what they want here. If your hospital participates in a risk adjustment program where revenue can be impacted by the acuity of the patients, then it may be essential to capture every chronic condition mentioned in the record even if not directly mentioned as treated in the current encounter. On the other hand, your facility may be more concerned with coder productivity and not want their coding staff to be investing a great deal of time hunting through the record for every possible condition. Your managers and lead auditors, with the input of finance and contracting, should make these decisions based on the hospital's payer contract requirements and financial priorities, and then communicate this to the coding staff in written policies.