If your object doesn’t show in the small thumbnail in the catalog, it may be because the new object is larger than the one cloned. The game may have a setting in the CRES defining how big and where the thumb should be drawn from. To get the game to draw the thumb from the bounding box of your object you will need to delete the array in the CRES that the game is using to create it’s thumb from.
Select CRES in Resource List
Select the 0x1:thumbnailExtension in the Blocklist dropdown box
Select the array in the Items box
Press Delete button