I really can’t thank you enough!
I’ve connected my event tick to the Set Spline Points and set Loc1 to 0 of the Make Array and Loc2 to 1. To me it makes sense, but to the engine it does not - nothing is visible. Disconnecting from the event tick shows the spline mesh where I’ve put it by default in the Viewport of the BP.
That’s right, I am tracing the (red) laser every frame.
Spline and Mesh are set to Movable.
World / Local coordinate space is set as per your screenshot.