Set Project as Parent for custom record Type when Advanced Projects feature is disabled

1. Navigate to Customization > Lists, Records, & Fields > Record Types.
2. Edit a Record Type.
3. Click on New Field.
4. Set Type to List/Record
5. Set List/Record to Customer.
6. Set Store Value to True.
7. Set Record is Parent to True.
8. Click Save.

Projects can only be accessed via the customer record and is treated as a customer if the Advanced Projects feature is disabled. Common mistake is selecting Projects as List/Record for the custom field.