Why are a lot of nodes not visible when I'm overriding a BlueprintImplementableEvent const function?

I have a BlueprintImplementableEvent const function in which I need to get a reference to the player’s Actor. I’ve seen a lot of tutorials on getting references to specific actors and most of them recommend using the node “GetPlayerCharacter”, “GetPlayerPawn” or “GetAllActorsOfClass”.

However none of these nodes is available when I right click in the empty space of my overriden function graph. And yes, I have ticked off the Context-sensitive tick box.
When I open the level blueprint for example all of the menitioned nodes are there… so that leaves me to guess that the context of my function (again, const and BlueprintImplementableEvent) doesn’t allow me to use these nodes.

And if that’s the case how should I achieve what I need - get a reference to the player’s Actor?