Solution : https://service.sap.com/sap/support/notes/535645 (SAP Service marketplace login required)
Key words :
function module bbp_nonr3_vendor_create add parameter it_taxnum directly, structure change function module bbp_nonr3_vendor_create, reference type dfkkbptaxnum select optional, function module create text symbol, german law gazette part, maintain structure bbps_nonr3_input_partner_x append, tax numbers/types' change, creating/changing tax numbers', maintain structure bbps_nonr3_input_partner append, structure extend structure bbps_nonr3_input_partner_x