Actors can only be seen in the play mode, it shows nothing in edit mode...It is strange...

In the project EpicZenGarden, there is a tree can be interacted to blossom, I’m trying to learn the whole logic, everything seems to go well, but what confused me most is that the tree can only be seen from play mode and it doesn’t display directly in the edit mode. Some rocks do the same way. I checked the relevant blueprint class, no one make this work. Can anyone give me some idea about it?