I had never wondered anything about this, but how could I skip arguments when calling a function?
my_function(4, b, 6) # How to skip 'b' argument?
func my_function(a = 1, b = 2, c = 3):
return a + b + c
I don't think that is currently possible in GdScript. This is usually made possible by named arguments which is a functionality in many programming languages but not yet supported in GdScript. I believe this pull request is the one you should follow to track when it gets implemented/merged.
You can do a manual implementation of it if you really want, the way to do it is to have your function receive a dictionary as a parameter and you check if they were passed or not to decide if you want to use the default or not. But it might get annoying with having to build a dictionary every time you want to call the function.