I definitely agree with this idea! It would be very useful to have association functionality in Workflows.
Insycle (full disclosure, I work there) allows you to associate in Workflows. Insycle allows for you to associate contacts, companies, and deals, in bulk, using any field in your database as a matching field. You can also manage primary associations/labels/child-parent associations.
Then you can add an Insycle Recipe into your HubSpot Workflows. Here’s an example of what that would look like:
