Hi Cephus, the about:config preference you mentioned controls whether the toolbar button drop-down panel pops open to show download status. But that isn't where you control what Firefox does with a download.

The Settings page has a list of different content types with the associated action. By default, most of them will say Save File, but do yours say "Open with" or "Use [relevant application]"? See: Manage file types and download actions in Firefox.

You can set browser.download.start_downloads_in_tmp_dir = true on the about:config page to make Firefox use the OS temp folder for downloads you open in an external application.

You can open the about:config page via the location/address bar. On the warning page, you can click "Accept the Risk and Continue" to open about:config.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox