Yes, We can create custom territories on a map by grouping existing locations or territories together.
Do you know? We use custom territories in Tableau as a separate geographic cluster field without modifying the existing geographic fields.
For instance, if on a map of India, we have sales for different states like Madhya Pradesh, Maharashtra, Gujrat, Chhattisgarh, Rajasthan, we can group all of these to create a single sales territory which will be a custom territory.