Hi @NArbel,
When you create a contact- or a company-based list (Menu > Contacts > Lists), you cannot only filter for contact/company properties, but also for deal properties:
Under Deal > Deal properties, you should find your broker property.
Once you save the list, HubSpot will populate the list with all contacts (or if you’re creating a company-based lists with all companies) that are associated to at least one deal that meets the criteria you specify.
Best regards!