list possible arguments / options for applications

From a Terminal session:

/Applications/Firefox.app/Contents/MacOS/Firefox --help

Usage: firefox [ options ... ] [URL]

where options include:

--g-fatal-warnings Make all warnings fatal

Firefox options

-h or --help Print this message.

-v or --version Print Firefox version.

-P <profile> Start with <profile>.

--profile <path> Start with profile at <path>.

--migration Start with migration wizard.

--ProfileManager Start with ProfileManager.

--no-remote Do not accept or send remote commands; implies

--new-instance.

--new-instance Open new instance, not a new window in running instance.

--UILocale <locale> Start with <locale> resources as UI Locale.

--safe-mode Disables extensions and themes for this session.

--marionette Enable remote control server.

--browser Open a browser window.

--new-window <url> Open <url> in a new window.

--new-tab <url> Open <url> in a new tab.

--private-window <url> Open <url> in a new private window.

--preferences Open Preferences dialog.

--search <term> Search <term> with your default search engine.

--jsconsole Open the Browser Console.

--jsdebugger Open the Browser Toolbox.

--wait-for-jsdebugger Spin event loop until JS debugger connects.

Enables debugging (some) application startup code paths.

Only has an effect when `--jsdebugger` is also supplied.

--devtools Open DevTools on initial load.

--start-debugger-server [ws:][ <port> | <path> ] Start the debugger server on

a TCP port or Unix domain socket path. Defaults to TCP port

6000. Use WebSocket protocol if ws: prefix is specified.

--recording <file> Record drawing for a given URL.

--recording-output <file> Specify destination file for a drawing recording.

--setDefaultBrowser Set this app as the default browser.

NOTE: This trick will NOT work for all apps. Firefox most likely works because it also has a Unix/Linux based version.

But it is worth trying:

app_name.app/Contents/MacOS/app_name --help

app_name.app/Contents/MacOS/app_name -h

If that doesn't work, then

strings app_name.app/Contents/MacOS/app_name >/tmp/tmp.txt

less /tmp/tmp.txt

and see if you can find an -something or --something strings that might hint at an option.

Then again, the option strings might be internationalized, so 'strings' may not find anything, as all the option names may be in the various language specific Resources files

I recommend that you drop into the Terminal and read the man page for open(1). Just because it offers an --args switch to pass optional arguments to applications, does not mean that the specific application is designed to accept them. Firefox is the exception, not the rule, and most graphical applications, including all of Apple's Cocoa-based applications, ignore the open --args arguments. The individual developer site will share, what, if any, command-line arguments that their graphical application may accept. Or they may not.

Some graphical applications may provide a separate command-line tool in their .app bundle that is run directly in the Terminal, and these accept their own arguments. Sublime Text 3, BBEdit, MacVIM, Open/LibreOffice, Inkscape, and Calibre are examples. These are not used with the open command.