The small Command Line supports auto-completion using the Tab key. For example, typing 'w' followed by Tab completes it into 'window'. Cycling through the possible completions is done with the arrow keys. Since Firebug 1.6 there's also an popup with suggestions shown for the entered part of a command.
The Command Line also supports the Command Line API, a set of special purpose commands.
To support the user analysing elements and writing code the small Command Line integrates an auto-completion for the commands you are typing. Therefore after starting to type a command you simply have to press tab and Firebug is completing the command. If there are several commands starting with the same phrase like "getElem" you can use the up and down arrow keys before pressing tab to alphabetically switch through all available commands. Thereby also the global variables, which you defined in your script, are used.
The entered script can be copied as bookmarklet via the menu of the Command Editor.
Shortcuts for inspected elements
The Command Line and the Command Editor offer you the possibility to easily access elements inside the DOM similar to the sizzle selector library integrated in the jQuery Framework. For a detailed description of the available commands see the Command Line API.
Inspect object in other panel
How you inspect elements using the console is described above. Besides that it's also possible to inspect them in the most appropriate panel by hitting
Shift+Enter instead of just
Enter. The console output also often contains links to other panels like the DOM Panel.