A quotation is not just an invoice that has not happened yet
Quotations get their own numbering sequence (QUO- by default), their own status lifecycle and their own template. They are valid for a period rather than due on a date, so the editor asks for validity instead of a due date, and the sheet says “Quotation” where an invoice would say “Invoice”.
Everything else is the editor you already know: the same items table, the same taxes, the same terms and the same branding.