> 1. GUI vs. CLI - I want to support both. But should it be a CLI first application that's then wrapped with GUI? Or perhaps it's better to build it as a GUI first application, and add a CLI interface to it? Or just have a core library, and use it in independent CLI and GUI tools? I never wrote a cross-platform tool, so I am not sure what's the best approach.

Don’t be GUI-first or CLI-first; be API-first. You can get started by writing a test target. As soon as you need more than “edit tests, recompile, run, examine debug prints”, you can start on both the GUI and the CLI together.

Focusing on keeping a solid API makes things much simpler. And if you ever regret choosing Electron over Qt or vice-versa, having all the juicy parts behind an API makes it much easier to switch.

For examples, look at Git, the TypeScript compiler, and Everything [0] (closed source unfortunately).

There was a quick-search app for macOS that used V8-to-Rust asynchronous procedure calls as the API. It would make a great example, but I can’t remember it’s name.

(Love the app idea btw! I look forward to trying it on my mess of files for my small business.)

[0] https://www.voidtools.com/support/everything/sdk/