If both devices are mapped to joystick slots, and their POV switches are set up, it should be possible to use a combination of one button/POV direction from each device to trigger a command.
Hold down the button/POV on one device, then press the button/POV on the other device, then release both.
The trial version is limited only in import/export functionality and profile/command count; All other features are available as they are in the licensed version.