editing an imported xls sheet

I have successfully imported an xls sheet, and following, attempted to add lines to the imported sheet via the view configuration section. My purpose is to input additional information to the imported xls sheet.

I have three matters:

i) One can readily add and change single line fields for data in the Configuration section. But only the first of these numerous changes in the editing/additions or Configuration section appears in the Views section. If I am doing it correctly, this then is a problem.

ii) I have an idea that even if one can add fields to the imported xls sheet data, it is not possible to later add information in the new fields in the revised xls sheet. Is this correct?

iii) If ii) is correct, then I think that I then have two alternatives. These are -

a) either add the additional data on the original xls sheets, and then import these?

b) start from scratch and create an entirely new form?