Is there a way of invoking a key combination over the CLI?
I mean something like:
$ invoke ALT+4
The cloest I can find in some quick Google searches might be something like xdotool.
What is xdotool? This tool lets you simulate keyboard input and mouse activity, move and resize windows, etc. It does this using X11's XTEST extension and other Xlib functions.
CTRL+ALT+L
to Lock Screen after X minutes