How to 'edit toolbox definition' of derived part?

I'm struggling to work out how to change the toolbox definition of a derived toolbox part (ie a toolbox part dragged into a part, as opposed to an assembly).

Usually, when in an assembly environment, it either gives you the option when its created or you can right click on the toolbox part and 'edit toolbox definition'.

Not so with derived toolbox parts. You can position it, but don't have access to any of the toolbox properties.

I suspect i'm missing something obvious.

Thanks in advance,

Tom

SolidworksToolbox