Use Open in Railyard...

If your talking about rolling stock or drivable vehicles, Railyard is the place to go.
Align the subject in a suitable pose & hit the Prt-Scr key, then go to your User Data/Screenshots Folder & use
IrfanView to crop & resize the picture for a screenshot...rename it $screenshot$ for quick ID.
Enter this into the config files:
thumbnails
{
0
{
image "$screenshot$.jpg"
width 240
height 180
}
}
If your talking about viewing a route, you will have to commit your Open for edit tab, then open a new Launcher & go into the game & manually find the route...
Using your previously opened CM, you can then find the object & view it's properties...
Enter this into the trainzoptions.txt file(before you start all of this):
-showkuids
That makes each asset you select show a kuid in the lower right-hand corner.
I would not however, make any changes whilst both CM & Trainz are open...