Adding specific vales to a filtered table

hi, for this specific case, you could create a calculate column in PowerBI with the next formula:

Region2 = IF( OR('Customer Table'[Region] = "North America",
OR('Customer Table'[Customer Name] = "Customer Nmae 7",
'Customer Table'[Customer Name] = "Customer Nmae 8")
),"North America",'Customer Table'[Region])

You also can create a flag column based in 'Customer Name' Column, and then create a formula with the region and flag column.

Customer Name        |   Region            | Flag (Based on Customer Name)

Customer Name 1     | North America  | 0

Customer Name 2     | North America  | 0

.

.

Customer Name 7     | Mexico              | 1

Customer Name 8     | Mexico              | 1

Customer Name 9     | Mexico              | 0

Customer Name 10   | Mexico              | 0

Region 2 = If( OR('Customer Table'[Region] = "North America", 'Customer Table'[Flag] = 1),

                             "North America", 'Customer Table'[Region])

Regards