And in Level Blueprint I want to fill array with these elements as you can see below.
Index of array should be ProtonNumber (because it is unique and it is number), and others parameters like Symbol, Name, Weight etc… should contain elements in that array.
What is a BP Element? A component, an actor? Anyway, you can’t directly compare a piece of text with an object… There is no conversion.
Your DataTable holds structs, you can populate your array with structs.
You can spawn (SpawnActorFromClass node) objects / components and feed them data from the Data Table and then add those objects / components to an array. I believe this is what you’re trying to achieve.
Yes, they spawn in the world - persistent level. Just keep it hidden.
If you just make an array of objects, it will be a linked list of null pointers since no objects were instantiated.
If you want pure data, keep it as a struct.
You seem to want objects, but you don’t want to construct them?