In the quotation, you can create custom fields, which are then available to you in your proposal template. Please note that your self-created offer template will not be automatically populated with the new fields. You must include these fields yourself in the database query and also in your report. Instructions on how to adjust the invoice template can be found here. You can also adjust the offer template XT_QUOTE in this way. You can not simply save the invoice template as XT_QUOTE because the database fields are different. So you have to adjust both templates accordingly.
In the next step, right-click on the heading of a custom field and choose Rename or Show. Here you can