Hi Mike,
I tried to replicate the steps you have listed down.
I did the following:
1) Create a report (e.g. Campaign report) and selected say 10 accounts for that report
2) Copied the sheets file using 'File > Make a copy'. The copied sheet has the same data as the original sheet
3) Tried to edit the report in copied sheet using 'Add-ons > Google AdWords (beta)'.
The menu does not have a 'Edit report' option yet, since the add-on does not recognize this as a AdWords report yet.
4) The only option in the menu is 'Create a report' which triggers the whole flow of 'selecting an account', 'configuring the report options using the right sidebar, e.g. choosing accounts, columns, report type etc).
5) Once you create a report in the copied sheet, you get an option to Edit report, which lists all the reports in the config sheet (newly created one as well as the one that got copied over). If you choose to Edit the report that got copied over, it also edits the original report from the original sheet.
I think this happens because when you did Make a Copy, it also copied over the report ID. However, I believe you can only edit the reports you have access to. If the user does not have access to the original sheet, it will error out. I will verify this with my engineering team though.
In the meantime, thank you for catching this issue and helping us make the add-on better and more robust.
We will be working to fix this issue, and keep you posted.
Have a nice day!
Best,