drawio/etc/sheetsaddon

For Deployment:

As david@jgraph.com use (see Tools, Script Editor):
https://docs.google.com/spreadsheets/d/1yUT6UE9bKDJCx7Kj1VEbrEaLyigcTO_bxyRXBDlFoLU/edit

Open the web app script in the script editor.
Make the changes you wanted. Test the code to ensure it functions as intended and is bug-free.
Click File > Manage Versions. Enter a new version description and click Save New Version. Click OK to close the dialog.
Click Publish > Deploy as Sheets add-on. Update the Project version to the new version you just created.
Click Update web shop draft.
In the new window, click on Publish changes.

If you get error "Sorry, unable to open the file at this time.", try Incognito mode.