Using SABnzbd 2.3.8 from Git source on Debian 9.8 and viewed with Firefox 65.0.1
The completed download permissions presently allow only one value:
The problem is: SABnzbd is not creating files with the provided value. This value is used when creating directories, but files are written using 666 (a sensible choice as it's generally undesirable to create executable downloaded files, whereas it's necessary to ensure directories are executable so they can be read).
Would it be possible to create a second field for file permissions, instead of adapting the folder permissions value?
The umask acts as a set of permissions that applications cannot set on files. It's a file mode creation mask for processes and cannot be set for directories itself. Most applications would not create files with execute permissions set, so they would have a default of 666, which is then modified by the umask.