Ah, I misunderstood your title line.
I don't recall anyone ever using the Command Line to open Monarch and leave it running on screen other than, iirc, when the User Input field was introduced and the Commands incorporated the ability to open the field for user input as part of the process.
I don't think I ever used that feature other than in testing and so my recollection is hazy. Even so my feeling is that it was only part of the automation process, not a means to opening Monarch and leaving it on screen.
For that all that was required for an input file and model load was a desktop short cut to a Project file.
Ten years or so back there were a lot of people in the forum using the command line approach but sadly most of them have either drifted away or, in some cases, are no longer with us. I am not familiar with what the latest CLI offers but perhaps someone who is can comment.
Presumably as a V14 user you will also have the Technical Support question option available to you?
This is the command I use to start Monarch, open a report and model then export and it works fine;
"C:\Program Files\Datawatch Monarch 14\Monarch.exe" /rpt:"\\ServerName\Shared\Today.txt" /mod:"\\ServerName\\ModelName.xmod" /exp:\\ServerName\Today.xls"
This is what I tried to do to start Monarch and open a report and model but not export, just stay opened;
"C:\Program Files\Datawatch Monarch 14\Monarch.exe" /rpt:"\\ServerName\Shared\Today.txt" /mod:\\ServerName\\ModelName.xmod"
The above command will not open Monarch, report and model, nothing seems to happen at all.