Hello all. My first post. The matter seems new here.
Dropbox is among the clouds that I have successfully linked Textastic for iOS to. Yet it doesn't show under the Open... command, nor under the subsequent More.. command to Manage Locations.
Tested on up-to-date iPad Air 2 and iPhone 7 Plus, and on iPad Pro 10.5" on latest beta iOS 11.
Customer support service by UserEcho