Since 2015 I have this idea of making one app that could be repurposed into a full-fledged app for all kinds of uses, like powering small businesses accounts and so on. Hackable and open as an Excel file, but more efficient, without the hassle of making tables and also using ids and indexes under the hood so different kinds of things can be related together in various ways.
It is not a concrete thing, just a generic idea that has taken multiple forms along the years and may take others in the future. I've made quite a few attempts at implementing it, but never finished any.
I used to refer to it as a "multidimensional spreadsheet".
Can also be related to DabbleDB.