Midlothian Council granted permission for the extension, comprising a distribution hub and associated works, in April 2018.
The council attached conditions including a requirement for "screen planting" along a fence "as shown in green" on an approved drawing.
In November, Midlothian refused a second application that sought to have the condition removed.
Earlier this month, the council's local review body considered an appeal from the supermarket seeking to overturn that decision.
In Scotland, local review bodies, made up of elected councillors, can review decisions made by officers under delegated powers.
An appeal statement prepared by consultancy WYG on behalf of Sainsbury’s advised that no green line appeared on the drawing in question.
"As a point of principle," WYG said, Sainsbury’s could not comply with the condition "because it refers to something that does not exist".
"There is, on the council’s online system, a ‘doctored’ version" of the drawing," WYG said.
"This plan was altered by the officer, without permission of the architect or applicant, and appears as if it was included as an application drawing, which it was not.
"It is our position that this is not acceptable. All plans submitted in relation to an application should come from the applicant or their agent.
"In our view, it is not within the gift of the local planning authority to alter plans without permission or to impose changes to the design - at least without discussing with the applicant first."
Midlothian Council's local review body rejected the appeal, advising that a fence approved as part of the supermarket’s initial application "was considered acceptable only on the basis that it would be screened by planting to limit the visual impact".
The council had not responded to a request for a comment from Planning at the time of publication but has reportedly denied that the drawing was doctored.
A spokesman told the Midlothian Advertiser: "It is quite common for a planning officer to edit a drawing such as this as part of a planning assessment, to illustrate requirements to an applicant. It was not altered or ‘doctored’ with any other intent."
Last week, a planning inspector rejected retailer Timpson’s plans to open a unit in the car park of a Morrison’s supermarket in Durham.
Last December, a High Court judge dismissed an attempt by supermarket Morrison’s to block plans for an Aldi supermarket and 221 homes in the London Borough of Hounslow.