Use case: find and document duplicates while systematic literature search

I know that JabRef can find duplicates. But I need some more and try to find out if it is possible with current JabRef.

Assume I search literature and different science databases. The content of the databases are overlapping. So some papers are in database A, some in B and some in A+B.
Assume that I have two export (ris, bib, whatever) files from the databases and import them to JabRef. This could result in two JabRef groups: “database A” and “database B”.

How can I go on from this point on?

I don’t want to only eleminiate the duplicates! It is important that I can document them because each step of the research process need to be documented. The point is in a real scenario there are a lot more then two databases. When looking at a specific entry/paper I want to know in which of the (multible!) databases it was found.

How would you (as a experienced JabRef user and maybe scientist) would solve that use case?

There are two issues as I see it:duplicates and the respective database. If you assign automatically a unique key to an entry like [authshort][shortyear] as key pattern, then jabref will find duplicates according to that key. The assignment should be done automatically so you do not mess it up. and [authshort][shortyear] does a good job so far as I have experienced. The other, more modern way would be to use the DOI identifier but that does not go back beyond ~2000 and not every journal in biosciences has labeled its entries with a DOI.

The database is a trickier way to go. I would add the name of the database (full name or abbreviation) as an additional entry in jabref. The unique key would find duplicates and the other db-entry the database. A report would indicate all the duplicate entry from the different databases.

My 5cts