Database column (inventory and like) with the collection number or filter it when you're looking to a specific expansion. Yup, it would time-saving feature to add, hopefully it would be appreciated too by many people.

Could you explain what you mean in more detail?

Ok i'm sorry, my english's not so good :/ For example, i want to import my "Dragons of Tarkir" collection through the "full card database", so i'd filter the entire database in order to show me only DTK cards. Then i would add a column in the sheet that would include the collection number of every card and let me sort the card list in order to get all DTK cards sorted from #1 to #264. This is the feature i want to see:)
So it's just adding "collection number" in the column button when i click on it.