Train travel Ljubijana, Croatia to Vienna

Yes there is a direct train from Ljubljana to Vienna. But you really need to look at a map of the area if you plan to visit.

I'm just seeing Flix buses and one other brand bus making the route in about 5 hours one way.

It's the return of the Emona train, departs at about 4pm, gets to Vienna at 10pm.

(see also the duplicate enquiry on another thread)

Just a quick heads up for future reference. Ljubljana is in Slovenia, not Croatia.

I'm just seeing Flix buses and one other brand bus making the route in
about 5 hours one way.

Where are you looking?

If you look on www.oebb.at, the website of the Austrian Railways, you will see that there is a direct train, and a few with one change.