Where can we see custom object which is created but not not updated on as tab? #

@Amit Kadpurkar, unfortunately you can’t add records without adding a tab.

There are couple of ways to do this.

1- You can do one thing, create your tab and don’t assign it to any app.

This way, from the App Launcher you can search your tab & add your records and also your tab wouldn’t display on the home page.

 2- Prepare your data in csv and upload it in your sandbox using DataLoader.

Hope this helps.