Hi Epic!
Would it to be possible you add more INEditor controls while editing arrays on DataAssets?
Until 4.7 we have just option to add a new element on the end of the array (Last+1) or do trash all…
An “idea” should be just add optional indexes to these operations, so if these are marked as -1 (default) they would just still make what they were designed for, but if the user inputs a value 0 >= they could do affect these specific indexes on the array, removing the element on the index or adding a new element at the specific index…
Unfortunatelly I suck on Slate/Editor extension, so I can just suggest/ask. 
Thank you!