There used to be one but it was replaced by another way of reloading the various URLs in entities editor (appending “?” or something along those lines to he URL). However, this other method was subsequently removed without reinstating the original reload button for entity scripts.
The Interface functionality to support an entity scripts reload button still appears to be there: you can test by using the reload button that’s in my entities editor to confirm.
Note: Interface appears to automatically reload file:/// scripts on the fly, but a “reload” button is needed to reload http:// scripts.