Am afraid I don’t understand the use case.
1. You wish to have a generic product in sales order, but manufacture a variant? - Yes this is possible
2. You wish to have generic product in SO but invoice a variant? I think this might not work, you would only be able to invoice what is on the SO
3. SO for a variant, manufacture the variant and invoice variant. Yes a possible in default flow.
Also, on the inventory managing a variant would be standard.
Hope this helps

Thank you again for sharing your ideas,

1- Yes and build a visible link between the SO (unique with generic) and the MO (one or multiple variants)
2- I wish to have the same generic product in quotation, SO and invoice.
a. Once a quotation is validated the Delivery button appears
b. I understand that I should enter the variant I would like to deliver (to updates inventory +
tracking)
c. Then I wish to send the invoice to my customer but a line with the variant appear in the invoice

Do you think doing 2.b is the wrong approach?

Best,

The delivery order created by SO would be reserving and expecting to pick the product selected on the SO. If a generic product is on the SO delivery order is expecting to pick generic product, if product variant is selected on SO, delivery order is also a variant.
It is possible to add additional products to the delivery order. If the delivery order is for generic product but you wish to pick a variant, add the variant as new line. On validation the SO would be updated with a new line for the variant.

I would believe the recommended approach is to have the variant defined on SO, create delivery and MO for variant (a single BoM for all variants). On validating the delivery create invoice for variant

It is possible to have SO for generic product that creates a draft MO, where the variant BoM can be manually selected. However the delivery order would need to be updated with the variant pick. On validation the delivery order would update the SO with additional line for variant. If your invoicing policy is set to ‘delivered qty’ the invoice would be for variant.

Hope am able to articulate the process flows. Can’t provide specific solution as I don’t understand your use case. Thanks