(press button to loot) What EVENT is this?

[muenchhausen]

Hi everyone!
I still haven't progressed with my LUA-skills, so I humbly ask for assistance, how to trigger a function at this event.
EVENT_RETICLE_HIDDEN_UPDATE only works after interacting.

So far I have only found addons reacting to loot pickup, but I like to pick up all loot automatically, to have a clean UI in combat.
I'm grateful for any hints.

With kind regards and thanks in advance,
Muenchhausen