The easiest way to "interact" with a hud is to incorporate letters or numbers into the hud which can be activated with the SCANCODEKEYPRESSED condition.
So if you have p.e. a teleporter with a script that shows a hud like:
Mars <Press M>
Venus <Press V>
Earth <Press E>
it needs to incorporate lines that move the player to different levels when the keys M, V or E are pressed.
It's not the same as moving the cursor over the buttons and actually "click" them but its quite reliable
In case you find my grammar and spelling weird ---> native German speaker ^^