Welcome,
DragScript is not a real script but a Drag&Drop facilities to run simple to complex automation.
The way you found is correct… you can retrieve and load decimal variables from external script call, Voyager is able to save the stdout of an external script to a decimal variable.
For save out of DragScript there is not option at now, but if you want you can analize the log, this is something similar to what Vitali have done for other porpouse here:
I will add, on external script parameters, values reading from decimal, this will be a nice thing. Thanks.