There’s already an event called “Snap Found” which fires when the snap point is found.
The movement of the preview actor is controlled by the UpdatePreview function, so if you want to add an event that fires when the preview reaches the point you can add something like this to this function:
It simply checks if the actor has arrived at the target location and fires the event. The Update function itself is really simple, it’s just doing TInterp between current and target transforms of the preview. If you want you can replace TInterp by something else, for example you can do a “lerp” driven by a timeline, so when the timeline is finished you know your preview has arrived at destination. The preview was made as a bp so people can easily modify it without touching c++