How to create views tabs in D8?
I have just created a views page with tabs. Following are the instructions.
Add a views display of type page


Set its path to "/test"
Then its menu option: Select "Default menu tab" and on next screen    select "Already exist" under the "parent menu item".
Then adds another page display
set its path to "test/tab1"
and in its menu option: select "Menu tab" and save.


Visit the "/test" page and both tabs appear.
Hope it may help you.