No. If you add columns in an existing sheet, just force a reload in the app builder to take them into account and be able to linked components to these new columns.
What David explained, it’s that when you create your app the first time, the existing tabs are loaded. Then, if you add new tabs in your Google sheet, they will (hopefully) not be added to your app automatically. To use them or display them, go to the tab section of the app builder, then click amon the + icon, add your new tab. You can give it a name (not mandatory) and an icon (preferably).
After, if you delete columns in your existing Google sheet, take care FIRST to remove any component linked to these columns. Else Glide will detect an issue with your sheet.
Hope this will clarify…