How To hide a Team on your Team Site (desktop):

1. Log into your Team Site
2. Go to Teams > All Teams.
3. Toggle the green eye icon  to red.
4. To un-hide the Team, toggle the red eye icon to green.

Result: Your Team will not display in your Current Teams list.

How to hide a Team on your Team Site (App):

1. Log into your Team Site App
2. Tap on Menu icon
3. Tap on Account
4. Tap on Team Visibility
5. Tap on desired Visible Team to hide
6.  To un-hide, tap on desired Hidden Team to make Visible

Result: Your Team will not display in your Current Teams list.

Note: Team Sites can not be deleted.