I am running Devonthink on the Mac as well as iPad and iPhone.
I have a folder in iCloud that I have indexed and the folder contains txt files that have filename extensions of .swift
These files can be seen in the file view pane on the mac as well as on the iPad. Under the filename in the iPad it says they are plain text and the size.
The problem is that by the iPhone it says that the file is unknown and does not appear in the file view pane.
If I share it I could open it in a different app.
I would like it to be seen in the file view window like by the iPad
There is no support for arbitrary extensions like this in DEVONthink To Go. In DEVONthink you can add additional plain text extensions via a hidden preference, but there’s no such mechanism for iOS.