Please create a multi-text control (free text, no selection) like this:
http://docs.webix.com/samples/60_pro/02_form/01_multitext.html
None of your current widgets does this, and simulating it with a listview, a multi-select or even a one-column grid is not a valid option for such an otherwise simple control.
The control is meant to store and return an array of arbitrary values, but ideally it could be extended to use any type of sub-control, like date-pickers for multiple dates, masked text boxes for structured values, etc.