Custom Field type Table

Hello. I need create a Custom Field type table from several tables and an unattached field to any doctype. Is this possible in ERPNEXT? Thanks

i understand this part, and yes you can create a custom doctype with type child table
and link it with any doctype in the system as a table .

Thank you, but it is not a new doctype, it is a personalized field where I can associate on sale invoice the item with VAT and a description