Appending Field Value to a Many to Many Connection Field with Column Actions

Hi, I am trying to create a form that tracks a list of Employees in different Business (many-many). When a new Employee creates an account, they can submit a request to be added as an Employee of a certain Business. Existing Employees of the Business can approve or deny their request.

When an existing Employee approves a request, I want a table action to append the requesting Employee (stored as a field value on the request form) to the existing many-many connection field connecting Businesses to Employees. This is not supported by Knack, and old forum posts from have suggested this might be possible with Javascript.
link to screenshot

Any ideas? Thanks