make a selection from combo ... display different input text fields based on the selection

Hi Everyone: I created a combo with 4 selections… how can I display different input fields based on different options?

You can set onChange handler and from it call show|hide to show or hide necessary part
Also, check showBatch API - it allows to switch visible of multiple controls with one command.

http://docs.webix.com/desktop__visibility.html

I had done it using radio button (similar to visibility.html) but how can I do it with combo of 4 options?

It is nearly the same, just use onChange event instead of onclick
http://webix.com/snippet/a7fd638b