In the method getSheetTabData of SheetAPI, it allows user add new tab to the sheet. .
Here comes the code example
var newTab = {
name: 'Merry Chirstmas',
color: 'red',
position: 1
};
SHEET_API.addSheetTab(SHEET_API_HD, newTab, function(sheetId){
alert("ok, sheet tab is added with id =" + sheetId)
}, this, true);
For adding new tab, please define sheet name, color and position. The sheet name should be unique. If not, an error message will be popup. Sheet position is start with 0. If position is not defined, the new sheet will be added in the last position.