How do I add a custom mapping between Pipedrive and Vtiger CRM?

You can customize field mapping under the sync settings of the required module. 
Follow these steps to add a custom mapping:

1. Log in to your CRM account.
2. Click the Main Menu.
3. Select a module such as Contacts, Deals or Organizations. The List View of the selected module appears.
4. Click the Sync button. The Sync window pops up.
5. Click the Settings button beside Pipedrive. The Sync Settings open.
6. Click Field Mapping in the sync settings sections of the required module. For example, Contacts Sync Settings.
7. Click +Add Custom Mapping.
8. Select the required Vtiger CRM field from the drop-down.
9. Enter the required Pipedrive field name to map. For example, (data.field_name).
10. Click the delete icon to remove a custom field.
11. Click Save. A success message will appear.

Repeat the steps to add more fields.