AssetDatabase.AddToObject with existing assets

i have a huge amount of .asset files (ScriptableObject derived classes) that i now want to add to a collection (another scriptableobject derived class as .asset) to get rid of all the separate files (i want to be able to delete them after adding them to the collection).
Before i break things i wanted to ask this to be sure.
Can i use the AssetDatabase.AddObjectToAsset() with existing assets (the asset to add to the collection), or do i maybe have to instantiate that first to make it work or something like that?

Edit: i want to maintain the references to these objects if possible after they’ve been added to the asset.

if i instantiate it that would obviously create a new object, so the reference to it is not maintained, so what are my options?