Inventory CSV import add quantity all cards/replace quantity

It'd be nice to add an option to update the quantity field as opposed to force add to the quantity when importing a csv.

For an example:

I have my whole collection in delver lens.  Let's say that in my collection I have 4 Aven gagglemasters.  I generate a CSV and upload it to deckbox.  Cool 4 in my inventory.

I just got 2 more aven gagglemasters! I scan two more into the same delver lens collection generate a CSV and upload it to deckbox.  At this step I'd like to be able to pick between updating the quantity of aven's in my inventory to reflect the new CSV value, OR to just add that many. 

In option one i.e. update the qty, the deckbox inventory would change to 6
In option two i.e. add the qty, the deckbox inventory would change to 10.

Thanks!