Q: Can a retiree include his or her former organization as an affiliation on a manuscript?

You can definitely submit a paper to a journal as an author or a co-author whether or not you are associated with any organization/institution. 

Regarding the affiliations, since you are a retiree, you can choose between these two options:

1. You can choose to publish your paper as an "Independent Scholar" and not include the name of any organization in your affiliations.

2. In case you started the research when you were an employee of the organization and your work was funded by them (at least in part), then you can list yourself as a retired employee of the organization in the affiliations.

However, different journals may have differing rules about affiliations. So it would be a good idea to write to the journal you are planning to submit to, explaining your situation in detail, mentioning what kind of support (financial or use of resources) you have received from your previous organization, and asking them if you can add the name of the organization in your affiliations.