There is number of questions here, I’ll try to explain in genreal - You don’t have to use anything from trap BP logic. You use only save game and load game functions like in video. If want to save something specific, to need to pass it into save game function which has struct as a param. But if you want to make just a checkpoint (so progress will be reset when you will exit the game) you should do it differently I think. Idea from top of my head - make a volume which will cover all area between checkpoints - lets say from level start to first checkpoint. On begin play, in level script use function get all overlaped actors of class and as param, use this volume. As a class you set for example health pick up. This way you will have an array of all health pick up. Get location of each of them. Then when player dies in this first section, destroy all health pick ups that you collected at begin play, and spawn them again with locations that you store in array. You can do it for other classes and all level this way. And when player died in section 2 for example, (you can check it for example by checking if checkpoint is activated.) you respawn BP’s only from section 2, which will be covered by seperate volume.
Sorry from long answer 