tableau - Add a Calculated Row For Custom Subtotaling -

i'm trying perform custom subtotaling on sales data give total , non-us sales offices. worksheet looks table labeled "current" , trying make table labeled "desired result"

when tried group sales centers , non pill (dimension) greyed out. after googling through bunch of threads found grouping not supported secondary data sources. there anyway manual calculation in table calculations add row or custom subtotaling?

add column country (assuming have country in data) [see example had states , zip codes]

then go analysis > totals > check on show grand total , on add subtotals

visit calculations totals - grand total turn on more information.