In the part selection [Part selection] on the Classes dialog page, you will now find your newly created my_class1 in addition to the existing classifications Standards, eClass 4.1, etc. If you open the corresponding directory tree down to the lowest branch, you will find the part that you initially assigned to the my_class1 classification in PARTproject.

The small preview bitmaps (myclass_small.bmp) are used within the class directory tree, the large preview bitmap (myclass.bmp) is displayed on the Symbols tab page (if set).

"My Class System" in PARTdataManager