Adding a "Freeform" Note to a record...

Let's suppose I have an 11 yoa girl on my ward roster who was never baptized. She shows up in my membership audit every 6 months.
Let's suppose I reached out and talked with her mother and she (the mother) expressed no interest in the church. This child was given a name and a blessing as an infant by the Bishop of a friend of the mother. That is the only real contact this child has had with the church.
My intention is to move the record to the Address Unknown pile. How can I add a note to the membership record of said child to let anyone out there know that there is no immediate need to do anything with this record in the future?

General Handbook, 33.6.2, states;

GH, 33.6.2 wrote:A person age 9 or older who has a membership record but has not been baptized and confirmed is not a member of record. However, the ward in which the person lives retains the membership record until the person is 18. At that time, if the person chooses not to be baptized, the bishop cancels the membership record. The stake president’s permission is required.

The child's name appears in the unbaptized children list of the unit membership audit as a reminder. When conducting the membership audit and you are certain the child has not been baptized, then the name is not checked and there will not be an audit exception. The unbaptized children list is useful for ministering and finding efforts.

Using the Move Record Out feature in LCR > Membership to place the record in an 'address unknown' status at Church headquarters is not appropriate since there is communication with a parent and the household address is either known or can be obtained.

General Handbook, 32.14.5, addresses membership records with annotations. These annotations are for specific situations and require authorization from the Office of the First Presidency and do not include any provision for 'general' annotations or 'notes'.

And so you find yourself in a very typical situation, where there is valuable member information that certain leaders know, and that they desire to retain electronically for future leader awareness, and would prefer it be tied to the member somehow. While the specific rules and guidelines around this may evolve over time, the only realistic option leaders currently have is to store this data outside of Church tools, since there's no functionality provided by the Church for 'notes' (and the Church has provided no indication this is in their development plans). All the appropriate data safeguarding should be followed (GBH 33.9.1 and elsewhere).