Feature summary
The feature is a line below each entry that allows the user to control said entry with commands of QuickStatements from Wikidata (see image)

The edit rules of QuickStatements would apply for this:

• "+" - to add a Wikidata item to the list (eg. captured with (P4082): "+Q5033194" would add Canon EF-S 60mm F2.8 Macro USM (Q5033194) to the list)
• "–" - to remove a Wikidata item from the list (eg. captured with (P4082): "–Q5033194" would remove Canon EF-S 60mm F2.8 Macro USM (Q5033194) from the list)
• "+item|property|item" would work like the "Add qualifier" button (and vice versa with "–")
• "+item|Sproperty|Sitem" would work like the "Add reference" (and vice versa with "–")

Same applies "+ Add statement" button:

• "+property1|item1" should be more than enough to add the item.
• More than one property + item combo (eg. captured with camera + lens) could be added in multiple lines that you either copy from something like notepad/kwrite/gedit etc. or to add a 'new line' with the de facto standard of Shift + Enter adding another row of "+property2|item2"

Use case(s)
The use case is to make editing Structured Data easier and faster.

• Current workflow: Click edit -> click in "Search to add items" box -> insert item -> click item -> hunt for "publish changes" button (T410708) -> click "publish changes" button
• Suggested workflow: Insert command -> Press Enter (or click "publish changes" button)

Benefits
The user would save time and therefore be more effective. This would especially be a time saver if you don't have to search in the field for your item, but already know it and thereby everything more than the shortest way to add the item is time wasted.
Especially adding new statements via the "+ Add statement" button is actually quite painfull as there are even more steps and is even more waiting involved that could be done much faster with a oneliner.