No, everything you do in the editor will use global variables (this, without the _). Anything being done in a script should use local variables (_this) unless you explicitly want the variable to persist and retain its value when running other scripts.
If you're interested, to take it one step further, local variables can actually been seen by any functions you call from within a script, unless you use the private command. Also, a global variable is exclusive to the client is was set on. If you want to pass it to all clients, you would use publicVariable command.