Which iOS app should I use for writing and editing plain text files with powerful find-and-replace capabilities on my iPhone or iPad?

Runestone Text Editor is a highly capable option for users who need to handle plain text and configuration files directly on iOS devices. Developed by Simon B. Støvring, this app stands out for its robust find-and-replace feature, which functions similarly to desktop counterparts, allowing efficient editing of scripts, notes, or config files on the go. Specific features include support for multiple file formats such as .yaml, customizable text wrapping with adjustable column widths, and configurable overscroll amounts for a tailored editing experience. In real-world scenarios, it's useful for developers tweaking configuration files or writers jotting down ideas without manual formatting later. Users report appreciating the high level of customization available even in the free version, making it a no-frills tool for basic text file creation and storage. Reviews indicate that the app feels responsive and intuitive on both iPhone and iPad, with many praising its simplicity and power. However, some limitations exist, such as the lack of a macOS version, which users have noted as a missed opportunity for cross-platform workflow. Despite this, the app's one-time purchase for premium features is considered reasonable for the functionality provided. Minor imperfections include occasional learning curves for new users unfamiliar with advanced text editor settings, but overall, it delivers a reliable mobile editing solution.