Create a Custom Record Field of List/Record Type That Source All Custom Item Fields

1. Navigate to Customization > Lists, Records, & Fields > Record Types > New > Create a Custom Record.
2. Use Name=Test and hit Save.
3. Create a custom record field with the settings below:
• Type = List/ Record
• List/ Record = Field
• Store Value = T
• Under Sourcing & Filtering subtab > Filter Using = Script ID / Compare Type = contains / Compare Value = custitem%
4. Hit Save.

Note: This works provided that there is an existing custom item field and the custom field ID starts with custitem.