Add Custom Field as Column in the Billable Time Subtab of an Invoice Form

To create the custom field, perform the following steps:
     1. Navigate to Customization > Lists, Records, & Fields > Transaction Line Fields > New.
     2. Provide a Label.
     3. Select the Type.     
     4. Check Store Value.
     5. In the Applies To tab, check Time and Group on Invoice.
     6. Click Save and Apply to Forms.
     7. Select the form where to apply the field. Check Show for the selected form.
     8. Click Save.
To check the custom field:
     1. Navigate to Transactions > Employees > Track Time.
     2. Custom field displays in the Main Screen of the form.
     3. Navigate to Transactions > Sales > Create Invoices.
     4. In the Items tab > Billable Time subtab, the custom field appears as column.