Expose Working Copy as a Document Provider
Working Copy is such an invaluable resource on iOS because it is a Document Provider. In short, this means that other applications can edit files stored within Working Copy's container in-place. In practice, this means that text editors such as iA Writer can be used to modify files without pulling them into their iCloud containers. For years, I avoided using iA Writer on iOS because it had to pull all files into its own iCloud container. This is a massive improvement.
Working Copy's User Guide describes how to expose Working Copy as a Document Provider. Before anything else, take special care to follow the linked instructions on Apple's documentation about how to use third-party apps in Files. Afterward, follow the set up instructions for apps like iA Writer and Textastic.