If you are using Bash 4.2 or later, Zsh, or FiSH you can enable Tab Completion for the QMK CLI. This will let you tab complete the names of flags, keyboards, files, and other qmk options.
There are several ways you can setup tab completion.
Add this to the end of your .profile or .bashrc:
source ~/qmk_firmware/util/qmk_tab_complete.sh
If you put qmk_firmware into another location you will need to adjust this path.
If you want the tab completion available to all users of the system you can add a symlink to the qmk_tab_complete.sh script:
ln -s ~/qmk_firmware/util/qmk_tab_complete.sh /etc/profile.d/qmk_tab_complete.sh
In some cases a symlink may not work. Instead you can copy the file directly into place. Be aware that updates to the tab complete script may happen from time to time, you will want to recopy the file periodically.
cp util/qmk_tab_complete.sh /etc/profile.d