Anyone experienced with adding weight to toolboxparts ?

I'm trying to add the property weight to a toolboxpart but it seems like when having an assembly with multiple toolboxparts only the weight from the first configuration is returned.

Saving the toolboxparts as single files and adding the property weight is'nt a solution either, the 'smart' conexxion then with the toolbox then is gone.

I'm using "SW-Mass" as string and also tried "SW-Mass@@Default@socket head cap screw.SLDPRT"

How to handle this ?

Greetings !