For anyone else who is wondering about this, I’ve discovered that the Protect Scripts option is
available in the Library Creator Editor:
It’s not clear to me what the documentation that I linked to above was referring to, but it is good
to know that Script protection is available.
I would still be interested to know if protecting the scripts on a specific layer (rather than
globally) in a manner similar to the documentation linked above were actually possible,
since I think that might suit me better.