Use account.tax Tax model for discounts as well
Configure payable/receivable accounts on fiscal positions
Make the Notes field on fiscal position translatable
Add option to group invoice line per account
Hide analytic lines
In the supplier invoice, automatically update all products whose discount on the line is different from the supplier discount
Use the actual product price to calculate margins on invoices
In the supplier invoice, automatically update all products variants whose unit price on the line is different from the supplier price