var customFloatingObject = new GC.Spread.Sheets.FloatingObjects.FloatingObject("f1", 10, 10, 60, 64);
var btn = document.createElement('button');
btn.style.width = "60px";
btn.style.height = "30px";
btn.innerText = "button";
customFloatingObject.content(btn);
activeSheet.floatingObjects.add(customFloatingObject);
//takes effect when added into the sheet.
customFloatingObject.startRow(2);
customFloatingObject.startColumn(2);
customFloatingObject.startRowOffset(10);
customFloatingObject.startColumnOffset(10);
customFloatingObject.endRow(7);
customFloatingObject.endColumn(5);
customFloatingObject.endRowOffset(10);
customFloatingObject.endColumnOffset(10);