We recently tried the newly released sale_amendment and purchase_amendment. We think that it would be useful to add amendments from the sale itself but that is only possible when there’s already an amendment in the sale because otherwise it is invisible. See: http://hg.tryton.org/modules/sale_amendment/file/632e5e9794c2/sale.py#l17
I think the invisible state should simply be declared as: Eval(‘state’) != ‘processing’
Opinions?