Hey @michellemedd!
As you've already encountered, Airtable's record update automation action performs what are called destructive updates. These are updates that update defined fields exactly as defined in your automation configuration.
This is in contrast to your desired behavior, non-destructive updates, where the update action appends new data to any existing data.
While you cannot currently change this behavior, you can achieve the desired result by adding the existing values of the field to the automation action.
The easiest way to do this is by adding a new Find Records action prior to your update action. After your automation finds the record to update, you'll then insert the current value of the desired field into your Update Record action along with the new data you want to append.
There are a few interesting scenarios that you may want to plan for. I might recommend wrapping your Update Record action into a condition action group that proceeds only when a single record is found. Should your Find Records action return either no records or multiple records, you can implement a different set of actions (or none) to prevent an automation failure.
