CSV Import: Sales Order > To remove specific line item(s)

1. Create a CSV Import File with the following columns/values:
-Sales Order Internal ID
-Item Line ID (Refers to all Line Items to be retained)

*Users may create a Sales Order Transaction Saved Search to pull up above fields.
-Lists > Search > Saved Searches > New.
-Click on Transaction link.
-Under Criteria tab > Standard subtab > Add the following fields:
-Type = is Sales Order
-Main Line = is false
-Tax Line = is false
-Shipping Line = is false
-Under Results tab > Columns subtab > Add the following filters:
--Internal ID
--Line ID
-Edit the Search Title as desired
-Hit Save & Run
-Hit Export - CSV button to export the file.
-Modify the exported file to only show the row(s) referencing to the Item Line ID(s) to be retained after the import.

2. Navigate to Setup > Import/Export > Import CSV Records.
-Import Type = Transactions
-Record Type = Sales Order
-Character Encoding = Western (Windows 1252)
-Select One file to upload
-Next
-Data Handling = Update
--Under Advanced Options > Overwrite Sublists = True
-Next
-Map the following fields:
--Internal ID = Internal ID (Could be found under the Sales Order folder)
--Line ID = Items : Line Id (Could be found under the Sales Order Items folder)
-Next
-Enter an Import Map Name
-Hit Save & Run

Note: It is highly suggested to update one sales order record first to check on the result and for testing purposes.