If you're looking to add fields in quote line editor (or Quote Line Editor for short), here are the steps you need to take:
Login to your Salesforce instance and navigate to Setup.
Enter “Quote Line Editor” in the Quick Find box, and click the associated Quick Find result.
Select which fields you want to make available for editing in the Quote Line Editor.
Click “Save” when you’re done.
Note that in order to make changes to the Quote Line Editor, you’ll need to have the “Customize Application” permission.
Hope this helps! If you have any further questions, please feel free to let us know.
If you'd like to learn more in-depth tips, tricks and resources related to Quote Line Editor, you can check out this blog post:
<Link>
Thanks!