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Mathod: AcGiTransientManager::addTransient (AcGiDrawable *, AcGiTransientDrawingMode, int, const AcArray< int > &)
seems to draw transient the same way, regardles of second parameter- AcGiTransientDrawingMode. I tried to use "AcGiTransientDrawingMode::kAcGiHighlight" but transient graphic is not highlighted as it is in Autocad. (tested in Bricscad 2017 and 2018).
BTW, I noticed that drawing of transient graphics is not supported in Bricscad 2016 at all.