Not a GDL issue per se, more an Archicad wish. I’d like to be able to open an object with the current parameters of a placed instance rather than with the defaults. When there is an error in a complex object, it can be tedious to replicate the exact conditions of the error.
Just a tip (you may already know anyway): try to use the option “Dump Library Parts of Selected Elem” of the “Library Developer Menu” to list the stored and active parameter values into the Report window – but these do not apply themselves onto the opened libpart in GDL editor, so maybe not so much of a help, but at least the parameter values of the instance can be checked more easily. By comparing the active parameter set of 2 different instances, sometimes the source of the problem becomes clear pretty fast.
I just had to do the same thing for Parameter transfer from objects set by the client:
For this I wrote an export routine via GDL TEXT addon. The placed objects then can
export their parameters, which I replace in the XML-Version of the object.