Q1: What is the production account in v16 in product category?
ANS1: A production account is used during a manufacturing order for finished goods.
Q2: What is the production account in v16 in the inventory location (virtual location/production)?

ANS2: A production account is used during a manufacturing order for finished goods.
This has the same function as the production account in the product category.
Q3: What happens when different accounts are set in the production account in both the product category and the inventory location (virtual location or production)?
ANS3: Odoo prioritizes the inventory location (virtual location/production) account.
See the steps below.
1. First of all, if you can't find the inventory valuation under the product category, please review this file:
https://www.odoo.com/sl_SI/forum/help-1/v16-v17-where-is-the-inventory-valuation-in-the-product-category-234375
2. Go to the accounting app > configuration > settings > enable checkbox on Automatic Accounting.
Then you will see the general account, including the production account.

3. Create an account.
Go to the accounting app > configuration > chart of accounts.
Create an account with code 4545, an account named WIP Product Category. Account type: current asset.
Create an account with code 4546, an account named WIP Location Production. Account type: current asset.
4. Go to sales app > configuration > product categories (e.g., All).
Open a product category > set Automated on inventory valuation > Set a 4545 account on the production account.

5. Set the product category on the product template.
Go to sales app > product > open a product (e.g., FG) > Set product category: All (this is the category I set for the production account).

6. Inventory location
Go to the inventory app > configuration > location > remove the 'internal' filter > search for virtual location or production.

7. Set the 4546 WIP Location Production Account on both the incoming and outgoing accounts.

=====Time for testing=====
1. Create a manufacturing order for product FG and pull random storable products as components (with a cost of $0).
E.g. WH/MO/00009.

2. After a complete manufacture order, the automated journal entry is created for MO/00009.
As we can see, Odoo uses the 4546 WIP Location Production account instead of the 4545 WIP Product Category.
Conclusion: Odoo will prioritize the account set in the inventory virtual production location.
