1.
why is line separated (blank line) here ?No idea, we'd have to see your script to know that.
2.
how to bind it ?Bind it to what?
3.
how to input on another place this blank line ?If it's blank, why would you want it somewhere else?
If you mean how to create a 'blank line', well generally you can't but if you echo a single ^o (Ctrl+O) or any other control code, it will "appear" to be a blank line.
/echo -a (You could also try "//echo -a $chr(160)" which is a 'hard space' in most fonts)