I've got only 2 solutions at the moment
1. make a "DirectionHelpers" layers and place an arrows on it.
It could be done by hard-coded part or by third-made application using dxflib (open todo.dxf by dxflib->analyse directions, add DH layer->write header, all existing data, additional layer with helpers, tail-> Open out.dxf in qCad). Can you slightly modify main() body from dxflib-188.8.131.52-1.src\test\main.cpp
from testReading(char* file); testWriting();
to testReading(char * file, dxf); testWriting(dxf);
2. Modify and test community qCad and send you a patch (lines and arcs).
P.S. to p.2: Should I do-it-by-myself or qCad team can add "dark blue" squares to line and arc entities (for closed polylines "semi-dark blue" for the SECOND VERTEX could be a solution)?