To clarify, are you trying to assign a value to in "C-Script1" (e.g. g_data.a=123) and then read that same variable in "C-Script2" and expect the value set by "C-Script1"?
This would not be possible with multiple C-Scripts within PLECS. The variables in each C-Script are local to that script. Consider, how would one prevent the two scripts from writing different values to the same variable in the same time step?
Your options are to incorporate everything into one C-Script, one DLL block, or pass the vectorized signals between the inputs and outputs of multiple C-Script or DLL blocks.