In the screenshot above, all invoices, credits, and bills have been generated but there remains a balance of $12. How are we supposed to know where it came from?

In this specific case, I know where it came from because this was a single test in an otherwise empty database.

1. Sell qty 10 of an item
2. Purchase 10 at $9
3. Receive 10 at $9
4. Ship 10 at $9
5. Invoice customer for 10
6. Receive bill for qty 4 at $9
7. Receive bill for qty 6 at $11
8. Return 10 from customer
9. Issue full Credit Note

This results in the screenshot above.

Repeating my question above, how are we supposed to know where it came from? At least with v17 you got a Revaluation Journal Entry and you could piece things together.

Here's another scenario I haven't tested yet but has happened to us a few times: Receive a subcontracted good and ship it before completing the child MO and resupplying the subcontractor (side note: Odoo shouldn't allow this to happen). This also results in a revaluation  JE that can be tracked down with some difficulty.