Bit late to the party, but just wanted to add:
In past games I’ve usually made a system to save level stuff to DataTables that can then be easily referenced in game later (such as enemy positions, environmental lighting setups, etc). Only problem is that you then need to open the data table and manually click save for it to keep the changes.
Would be nice if there was a way to force assets to save, this way we could also use Editor Utility widgets as custom DataTable editors! 
And also the big one, an asset selector so we can do much more than just simple level tweaks, as it’s one of the few things that currently isn’t possible to get past using widgets.
Also! In the preview I noticed there was a widget that functioned identically to the details panel categories, however it was very buggy and removed in a later preview. Crossing my fingers that it comes back, as being able to hide content (similar to categories) is incredible!