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My startup is building a product in the spreadsheet arena, and I'm looking for a project to build that we can offer for free service as a sort of marketing initiative.

Given the nature of our app, I'm mostly considering ideas related to spreadsheet usage. The main one I'm thinking about is a simple landing page where users can upload multiple spreadsheet files and easily append the data into a single table/document (allowing for basic Pandas operations). My concern is that this idea isn't very strong, but I really want to build something.

Any ideas for simple-ish, useful services I could work on?

I'm building this on my own, so I'm trying to keep scope manageable.