A custom list is created in NetSuite with no values added. If there are many values to be added in the custom list, it can be done through csv import.
- As the first step, create the CSV file to be imported. The csv file should have 2 columns: column A for name of the custom list and column B with values to be added in the list.

2. Go to Setup >Import/export > Import CSV records > Select Import type = Customization > Record type= Custom List > Upload the CSV file > Import options = Update
3. Map the columns Name and Values as follows

4. Click on Run
The custom list will be populated with values in the csv.