How to delete a Segment with all its keys?

Question

Is there a way to delete a segment with all its keys in one action, rather than deleting each key individually?

Answer

It is possible to delete all keys from the Segment UI:

1. Locate the down arrow on top of the checkboxes column
2. Click on it, it will show two menu items,
3. Select all records from there, then "Delete" button will show up. 

Once the keys are deleted, delete the Segment definition from the lower dotted icon (...)

Then proceed to delete the Segment from the upper dotted icon: