A modest documentation...

Folders

Folder	Description
node_modules	NPM Libraries, see `package.json`
public	Built `svelte` front-end, done through scripts in `package.json`
src	Source files (svelte front-end, electron main, support node files)

File	What it does
App.svelte	Front-end entry point with actual content linking to /menu and /canvas components
App.scss	Any (S)CSS that doesn't have to instantly load should be here
controller.js	Communicates between `electron` and front-end, is importable by any svelte components. Put all `electron` communication here.
electron.js	Initialization of `electron`, incl. main window.
fsman.js	Manager for any file system operations, use node's built-in `fs` package here. Should only be imported by controller.js
store.js	`Svelte`'s way of state management, is imported mainly by front-end and sometimes by controller.js. Any operations should be done through respective functions defined in this file. The file should only import from "svelte/store". This is the main way to store volatile data.
svelte.config.js	Additional configuration for svelte to enable proper SCSS support.
svelte.js	Initialization of svelte handled by `rollup.config.js`
rollup.config.js	Is actually not in `src` folder, but above, handles svelte plugins, export and development state.

Folder	What it's meant for
src/canvas	Anything that has to do with drawing or visualizing mostly picture-based data.
src/menu	Anything that has to do with the little side menu for quick controls and metadata management.

File	What it does
.gitignore	Files/folders left out of `git` repository's version management, these include giant non-unique stuff like `node_modules` that can just be re-downloaded from `npm`.
concurrently.js	A script to run svelte development server alongside electron for live reload.
DOCS.md	Hosts this documentation.
package.json	List of dependencies used in this project (contained in `node_modules`), some license info and most importantly `npm run` scripts to get often used CLI stuff done quickly.
package-lock.json	`npm` auto-managed info for `node_modules` versions and some other stuff, it should not be `.gitignore`'d because it can apparently be useful (use google)
README.md	Some introduction for the GitHub repository.
rollup.config.js	Handles svelte plugins, export and development state, is the main entry point for building svelte through `npm run` scripts.

Search for "TODO" && "BUG" in all /src files.