According to this thread, the current TC icon work as above.TC9b12 now shows '!' as expected in all cases when OldListIcons=1:
If no iconlib is defined: '!' is overlayed with TC's internal overlay
If iconlib with '!' icon inside it (icon 49 and 50) is defined: TC overlay with '!' from iconlib.
If iconlib without '!' icon inside it is defined: TC uses icons with integrated '!' from iconlib (icons 9,11, 15, 18).
https://www.ghisler.ch/board/viewtopic.php?f=15&t=45252&hilit=hidden+icon&start=15
If the iconlib don't have the independent "!" icon, will use the iconlib's (9,11,15,18), that would even be the case when it is an packed archive. Would it be better if there is no "!" icon, fall back to use the internal "!" icon overlay?
especially by adding a new dim icon option. we don't even need "!" mark at for hidden file at all