You can create an order in the system with an order status: quote, setting titles and expiry status
Quotes are simply an order, with the status Quote. A quote if paid, will progress into a normal order status flow.
If a quote progresses to paid or shipped status, then stock is automatically allocated at the same time, so that the stock counts of the products will be correct.
Merchants can choose to manually allocate the stock to a quote via the notes screen.
Quotes may appear in some sales reports where the report is not limited to "paid" orders.
Plugin options
Quotes can be created via CMS by viewing the relevant member and choosing to CREATE AN ORDER.
When it comes time to create the quote, you can change the action to Save Quote via the dropdown option indicated below:
Sending the quote to the customer will send the order with the title Quote rather than Order or Invoice.