Custom Hubspot Properties

I require a set of custom properties to add to a company in Hubspot.

In my Hubspot I have company types which are clients, prospects and customers.

A client can have many customers and many prospects.

A customer can have many clients.

A prospect can have many clients.

I require a multiple select dropdown called "Client Assignment" for when a customer is assigned to a client(s)

AND

I require a multiple select dropdown called "Interested Clients" for when a prospect is assigned to a client(s)

When viewing a company which is a Client, i need to see the total number of customers being assigned under "Client Assignment" and "Interested Clients". I'd like to be able to click on these two properties to view the companies