The share plugin allows sending a file to Android and open it immediately. The same would be uselful Android->Desktop or Desktop->Desktop
Desktop-side this can be achieved with QDesktopServices::openUrl()
To implement one needs to:
In the Share plugin when receiving a file check if the network packet has "open" set to true
After the file is transferred if open is true call QDesktopServices::openUrl() with the file URL
You can trigger the file opening from another desktop device using "kdeconnect-handler --open file:///home/foo/file.txt"
For this it is useful to connect the desktop to itself via the loopback link provider. You can enable it by running "cmake -DLOOPBACK_ENABLED ." in the build directory and running make again.