Exporting tables with summary generates separate files in ZIP; suggest combined export format

[ryepezb1]

When exporting a table chart with summary row enabled, Superset downloads a ZIP file containing:

table.csv — the full table data

summary.csv — the totals or summary data

From a technical perspective this makes sense, but for end users, especially in non-technical environments (e.g., education, reporting), this export format is not intuitive or practical.

❌ Problem:
Users expect to receive a single Excel or CSV file with the summary row at the end of the table.

Having two separate files adds friction and confusion, especially when sharing or importing the data elsewhere.

[rusackas]

I'm moving this to an ideas thread, since it's a good idea, but not necessarily a bug. We'd welcome a PR or further discussion from any/all interested parties.