SimplyPrint doesn't force you to start prints via. the SimplyPrint platform, so you can start your prints just the way you want to - and don't worry, SimplyPrint will still monitor the print. You will still be able to follow it in the panel and getting notifications on the state of the print.

There are a few downsides to printing outside of SimplyPrint though;

You won't be able to see the name of the file being printed, in the SimplyPrint panel
No GCODE preview of the file
No GCODE analysis, also meaning no filament tracking