1. Go to Accounting > Configuration > Analytic Accounting: Analytic Distribution Models 

2. Set up based on your requirement and it have to be corresponded with all conditions (partner,product template,product) > then auto aa will be filled when create SO/PO/Invoice/Bills

3. There're all conditions based on your setup

1. if field product template filled and field product filled, then field product should be removed only if field product not in variant of product template

2. if field product template not filled and field product filled, then field product template must be relation of product template in product variant

3. if field product template filled and field product not filled, then domain field product just show variant of product template

4. If the product template is filled but the product is not filled, the analytic distribution record will be called to all variants, (all partner)

5. if the product template is filled and the product is filled, the analytic distribution record remains as intended. (all partner)

6. if partner is set and product template filled but the product not filled, the ad will be called to all variants (exact partner)

7. if partner is set and the product template is filled and the product is filled, the analytic distribution record remains as intended. (exact partner)