Give this a try: https://support.mozilla.org/en-US/kb/keyboard-shortcuts-perform-firefox-tasks-quickly

Please let us know if this solved your issue or if need further assistance.

Navigating within the Preferences page is a little odd. On Windows, I get this:

• Try the down arrow to see whether the panel changes from General to Search. If not, press the Tab key once to select General and try again. (I have to tab once.)

• Arrow down to Advanced -- there may be a delay on Applications -- and the pane on the right should change for you.

• Press the Tab key once to move to the next element and watch for a dotted outline around the current category (e.g., General, Data Choices, Network, Update, Certificates). If it doesn't appear, try Tab again. (I have to tab twice.)

• Then use the right arrow key (or left arrow key, if applicable) to select the desired category (Network). Firefox should display the panel automatically.

• Press the Tab key once to select the Settings button, and then press Enter to "click" it.

• Within the Settings dialog, down arrow will move among the radio buttons, and tab will move to the next control (e.g., OK). I didn't experiment in detail because I don't have any proxy settings.

The about:preferences page behaves like a normal web page, so you need to use the Shift key to go to a specific element, so Shift+Alt+E should work. It is annoying that you can't see where to focus is (left panel, tab bar on content), so you need to press Tab or Shift + Tab to see what happens.

Ok thanks, I was missing the Shift+Alt+* (E in my case) trick. Using only tab and the arrow keys is too slow. So what I do now:

Alt+E Alt+N Tab Down arrow 7 times Alt+Shift+E