In order to import a quotation with a note / section on the line, you need to use two different fields : 

1/ Field "Description" to indicate the title of the section or the note you would like to put

2/ Field "display/type" to indicate that the line you are importing is a section/note. 
            a. If it is a section, please enter "Section" in your import file (See number "1" from screenshot)

            b. If it is a note, please enter "Note"  in your import file (See number "2" from screenshot)

See below a screenshot of the Quotation in the front-end odoo : 

And for the import, it will be these fields (indicated in yellow) 

Warning : we here put ("order_line") as a prefix for the fields as we are on the sale order line. 
Also, in order to import SO+SO lines, you don't need to put each time the info linked to the SO. (e.g. we don't put 5 times S00080)