Hi Edson Yui, I can imagine how frustrating this is you expect a simple button to be there and instead you’re digging through menus trying to figure out why it disappeared.
The Switch Mode button is missing because Excel no longer includes it by default instead you need to customize the ribbon by selecting All Commands in Excel Options adding Normal View Page Break Preview and Page Layout View to a new group under the View tab since Microsoft replaced the old consolidated button with these separate commands.
Do you want the Switch Mode functionality for quickly changing between different worksheet views Normal Page Break Preview Page or Layout and or are you trying to toggle between different editing or calculation modes in Excel?
Best regards
Lucky