If you can skillfully use Flex Builder shortcut keys it could advanced improve your working efficiency.The belows are some shortcut keys which you should know.
Ctrl-Alt-Down: Repeat current line
Alt-Up: Move line (or selection) up
Alt-Down: Move line (or selection) down
Ctrl-Click: Go to definition (also F3)
Ctrl-D: Delete line
Alt-/: Word completion (cycles through possible matches)
Ctrl-Up: Scroll up
Ctrl-Down: Scroll Down
Here is a list of keyboard shortcuts that are useful when editing code.
Here is a complete list of available keyboard shortcuts.