The process is very simple:
When loaded, TOP Layout is able to intercept every operation of part loading from external libraries. During this phase, TL checks the name of the loaded .DWG file and the name of the folder containing it. It then verifies the presence of a sheet with the same name as the folder within the counting sheet. If the sheet is found, TL analyzes the DWGNAME column to find a match with the name of the loaded drawing.

If a match is found, the TL assignment mechanism is triggered:
All values in the intercepted row are assigned as attributes of the part (unless the initial letter is an UNDERSCORE (_), in which case the attribute is not assigned).