No. You need to reload scripts manually if you're not using the script editor.

Coincidentally, you can actually write a script to handle this, though:

Code:
ON *:APPACTIVE:/reload -rs filename.mrc


Or you can have that loop through $script(N) to reload them all. It will trigger whenever you switch back to mIRC, so you can comment it out when you're not writing code. Note that /reload doesn't trigger ON START/LOAD events, you would have to /load to get that.