Is there a redo keyboard shortcut?
Not directly in Bash, as mentioned already in another answer.
However, when editing more complicated command-lines, you might want to open it in an editor that can provide redo functionality (and more). Bash uses Ctrl+X Ctrl+E keybinding (when using default keybindings) or EscV (for vi keybindings) to open the current command-line in your selected editor (by default, Nano, in Ubuntu).
You can then use the undo/redo commands from your editor.
After editing the command-line, exiting the editor will execute the command.
To change the default editor system-wide, use:
sudo update-alternatives --config editor
To override just for your user, set the EDITOR environment variable to the path of your preferred editor.
Site-note: Do use caution with this feature -- As mentioned in this comment, any editor exiting with a success (0 return code) will cause the command to be executed in its last saved state, which could be unexpectedly dangerous.
See this answer for a potential workaround (which I have not tested personally). Also note that some other shells (Zsh and Fish, at least) do not execute the command on exit, but simply paste it into the command line, then requiring an Enter to execute. This is, IMHO, much safer default behavior.
