To add questions insert a row in the spreadsheet (where you want your new question to appear) add the details for the new question(s) and run the update process from the menu. That will add the new question to the bottom of the form. If you then put a Y in the update column for the new question(s) and run the update process again it will put the new question(s) in the correct place.
Put a Y in the Delete column for any question you want to remove then chose Delete from the Sidebar menu. If you later want to add the question back in you will need to clear the item number and create it as a new question.
You can change any element of a question EXCEPT the question type. Make your changes in the spreadsheet, put a Y in the Update column for any question you want to update and click the update button in the sidebar
You cannot change the Question type through the update process so to change the question type you will need to delete the existing question (using the procedure above) and then in the spreadsheet remove the Item ID, change the question type and run the update process to add a new question.
Cell C4 has a default value of No. If you set this to Yes the form will be updated every time a user submits a response. In that update the form header details will be updated and the questions you select will be updated (see Which questions to update - below). You can use this functionality to stop the form from accepting responses after you have reached a limit you specify (in cell Y1 of the spreadsheet).
Cell E4 has a default value of No. If you set it to Yes, Form Maker will create a timed trigger which will run a process to update the form every hour. You can use this functionality to stop the form accepting responses after a specified time and date (in cell W1 of the spreadsheet).
Cell G4 defaults to Selected Questions Only. You can use this to specify which questions to update with the Form Trigger or Hour Trigger. If you choose Selected Questions Only then these two processes will only update the questions with a value in the update column. If you specify "Update All Questions" the all questions will be updated when the form submit or hour triggers run
You can use the update features detailed above to make a shrinking or expanding list of form options for Multiple Choice, List, Checkbox or Grid questions. To do that you will need to use the Options Menu in the sidebar to generate formulas to populate the options list for those question types.
This link will open a spreadsheet, linked to a form which will show you how this works.