I already did, but no FSDT_Pushback_USER folder exists, so I was just wondering if its possible to create this folder without messing up anything?
Sorry, I haven't read your message carefully enough: you were asking about the Pushback specifically.
The Pushback truck is not included in the Paintkit, so there's no USER folder for it. Of course, you can create any folders you want manually, provided you understand how the folder structure looks like, but it won't be so easy to customize as the other vehicles.