Please consider adding OneDrive to the cloud service Connections supported in Textastic.

Microsoft is doing a good job of ensuring that support for their OneDrive service is present, stable and sufficiently feature rich on a range of platforms. I would like to use it as a replacement for Dropbox in several multi-platform use cases where Textastic makes the iOS view work well. I use MacOS, iOS, Android and Windows devices and need to access the same content across those platforms.

Google Drive is no longer a viable option and Dropbox is going in the same (incorrect) direction due to their lack of investment in keeping their platform specific apps working.

OneDrive looks like the solution, once Textastic supports it as a Connection.