You can add a Job and then a Sub Job under said Job.

Go to your Customer Center, and Select "Customers & Jobs." 

From there you want to right click on the customer that you wish to create a Job for, and then select "Add Job". 

If you have a customer who has subsidiaries this is helpful, because it would look something like this;

Customer: Job: SubJob = Main_Customer: Their_Subsidiaries: Job