Sales order form customization

Hello Everyone,

My customer has a requirement as explained below.

Currently my customer is using Filemaker Pro tool for generating sales order, sales invoice and many more.

So their requirement is, they want to have the same sales order Item table as available in order form in their Filemaker Pro to be present in the ERPNext.

They want to replace the existing sales order item table available in ERPNext with their item table as shown in screenshot.

How can I do that.

Screenshot of Filemaker Pro attached below.

They want to select the variants with sizes and other options from the sales order itself rather than creating the variants in item master and then using it in the sales order form.

Can anyone suggest me on how to do this in ERPNext.

Thanks & Regards,

Would be better if you post it as a job on the portal. This does not look like a simple task.