Toradex is aware of the lack of command line support for the Toradex Easy Installer. We plan to implement it at sometime in the future (see #24297).
As a work around, you can use the autoinstall feature as documented on the Toradex Easy Installer Configuration File page. To get a serial feedback you can use a wrapup.sh script with the following content:
#!/bin/sh
echo "Production flashing complete" > /dev/console
exit 0
This will print the string Production flashing complete to the serial console once flashing finished.