1. To remove any unwanted Tabs from your App, hover over the Tab Menu and select Remove from App it and select the "X" icon.
This will move it to the "Inactive Tabs" toolbar on the righthand side. This will not completely delete the Tab and it's content. If you think you may use this Tab again in the future, keep it here.
2. To completely delete a Tab and all of it's content, it must first be in the "Inactive Tabs" toolbar. Hover over the Tab Menu, click Delete and confirm. This cannot be undone.