How can I get Quartz Composer to save files after the first time? I'm learning how to use Quartz Composer (Version 4.6 (151.1)) running on Yosemite (10.10.5 (14F27)).

I can successfully create a Quartz Composer document and save it to any folder.  However, after editing the document subsequent attempts to save it yield an error "The document “Untitled.qtz” could not be saved."  How can I get Quartz Composer to save the updates I make to the document?
After some trial and error, I discovered that Quartz Composer has a problem with directories that have a Spotlight-related entry in their Access Control List (ACL).

Using Terminal, you can see if a directory has a Spotlight ACL entry with ls -dle and looking for output that contains a _spotlight entry, e.g.:

$ ls -dle ~/Documents
drwx------+ 303 userx  staff  10302 20 Aug 12:21 /Users/userx/Documents/
 0: group:everyone deny delete
 1: user:_spotlight inherited allow list,search,readattr,readextattr,readsecurity,file_inherit,directory_inherit


To get Quartz Composer to save to the directory more than just the first time, remove the Spotlight entry from the directory's ACL with chmod, e.g.:

$ chmod -a# 1 ~/Documents


(here we remove the entry whose index is 1, which corresponds to the _spotlight entry gleaned from the ls -dle command).

Another way to do this is to use the Finder's "Get Info" menu command.  You will see a '_spotlight' entry in the "Sharing &amp; Permissions" section.  Select it and click the "minus" sign button to get rid of it.