Hello Yoottauva98
This is unfortunately not possible, as neither assembled bikes nor bikes wrapped in bags are accepted on the EN to Ljubljana. The bicycle must fit in the overhead bin made for hand bags where only foldable bikes will fit, if at all.
On the Railjet day connections to Austria, bikes in bags can be transported, however.
https://www.nightjet.com/en/angebote/fahrradmitnahme
Kind regards,
Roland