Changes made in Transform Sample File not changing in my Master Query

Hi blackanese27 

You may have figured this out already as your question is from a while ago.  However, if the below helps you or answers your question (or someone else's) it has served some purpose. 🙂

If I've understood you correctly, you have imported data from a folder and done some transformations (in the "Transform Sample File (1)" for example), and these changes are not getting reflected in the combined output file - right?

If the above understanding is correct, I believe it's due to an issue in Power BI where the "Transform File (1)" function linked to "Transform Sample File (1)" isn't getting updated/refreshed regularly enough.  Therefore the code in the function "Transform File (1)" - (which may not be updated after the "Transformed Sample File (1) has been edited) is still the old code powering the refresh and hence the instructions for combining the files; meaning your changes are not reflected.

To fix this, the only solution I've managed to find for now is clicking on the function "Transform File (1)" and then manually updating the code (very carefully and only as needed) via the "Advanced Editor"  or the formula bar window.  This does require you to know the coding side a bit and ensure all syntax is correct. 

Once this is done, when you "Close and Apply" your changes, Power BI will re-evaluate the function(s) that has been updated and you should be able to see all the changes you made manually reflected in the output.

Hope that helps!