[cldellow]

Google Sheets has an extensibility system: you write a React app that renders as a sidebar inside the sheets UI. This exposes a few additional API endpoints vs the vanilla sheets API. For example, you can determine the selected range, when a user has edited a value, changed sheets, etc. We use this in our add-on to help people select a range. Sounds like it might help for you, too!

The extensibility system also lets you show a modal dialog, which we use for previewing API calls to third party HTTP servers -- sounds like a similar thing could work well for you, too.

You could also look at supporting named ranges if you don't already, so people can refer to a range as `FinanceData` instead of `Sheet 1!A3:F90`