Show Manufacturer Tariff from Item record on Purchase Order line item

A. Create a Custom Item Field

1. Navigate to Customization > Lists, Records, & Fields > Item Fields > New.
2. Provide the Label, e.g., MFG#.
3. Set Type = Free-Form Text.
4. Mark Store Value.
5. Under Applies To tab, select item type/s.
6. Click Save.

B. Import a CSV file to input values on Custom Item Field

1. Create an Item Saved Search that will show Manufacturer Tariff and Internal ID.
2. Export the results as a CSV file.
3. Import the CSV file using Import Assistant and map the Manufacturer Tariff values against the field created from Step A.

C. Create a Custom Line Field to be applied on Purchase Order

1. Navigate to Customization > Lists, Records, & Fields > Transaction Line Fields > New.
2. Provide the Label, e.g., MFG#.
3. Set Type = Free-Form Text.
4. Unmark Store Value.
5. Set Applies To = Purchase Item.
6. Under Sourcing & Filtering:
    * Source List = Item
    * Source From = Name of custom field from Step A
7. Click Save.

Note: There is an enhancement filed already for this request under Issue 140971.