You can use the asJSON expression.
Add an textbox and a event like this:
--- textbox: set text to particles.asjson
The copy the text in the textbox into your favorite text editor and replace all the " with '. Then add " to the beginning and end of it, and select it all and copy it.
Now in your game you can remove the textbox and that event and add a event:
on start of layout
--- particles: load from json ...
Just paste the copied text instead of ... and voila, it starts pre-running.