They need to tweak their labeling

In order to save a file to your computer so you can access it later, when celtx is open, you need to go to File > Move To…, and your Finder will pop up so you can save it to reopen in the program later. I don’t know why there isn’t an alternative way around this, but from what I’ve found by poking around the app, it’s the only way to save… Hopefully this helps some people out!

Dianna_L about celtx script