I'm not expert, so maybe my suggestion can not to work. 
Import will return the new #st{}, then maybe you just need to update it by send that information to the main geometry window who handle most the command messages:

Import will return the new #st{}, then maybe you just need to update it by send that information to the main geometry window who handle most the command messages:
Code:
...
St = wings_import:import(E3DFile, St0),
wings_wm:send_after_redraw(geom, {update_state,St}).