To do this you just have to separate the Sales Orders that you use for Quoting the Customer with the Sales Order that you use to Bill the Customer.

The Sales Order that keeps track of the Time logged on a Task and any Products added is tied directly to the Task via the Sales Order field. [1]

The Quotations smart button shows all Sales Orders linked to the Task. [2]

So each time you need to send the Customer a Quotation for work (not the actual work) you would use the NEW QUOTATION button.  Do this for each of the six Quotations you want the Customer to review and sign.  Add the products and/or services so they can see the options or the initial quotes for the initial, additional and final job amounts.

You don't deliver any products or record any time against these quotations.  You just cancel them, as they have served their purpose (to tell the Customer about the option, to show them the price for the service and/or products suggested).

Based on what they decide (which of 1,2 or 3 they pick and what initial, additional and final work is performed) simply add the products and/or services that you need to the Task via the Products smart button:

This actually creates a 7th Sales Order.  You can do this at the start of the Task (as soon as you start Billing Time) even before you have created any other Quotations.  You will always have a single "final" Sales Order linked to the Task.

This 7th Sales Order is the one you end up creating an Invoice from.

The first 6 Quotations will not show up in the Orders to Invoice Menu because you did not deliver any of the products and/or services on them.