How to edit some system data records

Hi,

I have a report that is based on data from an SQL db. It gets refreshed weekly. On average there are about 2000 new records added per week. Of those 2000, maybe 100 necessitate having a single cell per record revised. i.e. an incorrect entry was made by a field agent: 'open' should have been 'pending', etc. (in reality there are about 40 different options for this particular cell/field). It is always the same field that would need revision, no others. Call it column A.

What would be the best way of accomplishing these revisions? I've tried downloading the entire db into an Excel file, then, going forward, adding the new records also via download each week, eliminating the invariable duplicates, updating the relatively few records that require it, and finally having Power BI query the Excel spreadsheet, and ignoring the system data entirely. This is a tremendous effort.

I was hoping that Power BI had the ability to create a new table based on the original system data table with a single additional column appended, Column B. The revisions would be manually data entered into said column, and if a cell had no value, copy over the value from Column A I would then remap the visuals to draw data from this new 'cleaned' column B, rather than the original column A.  I cannot seem to get Power BI to do this however. Any help would be appreciated.