Keep Helper lines
script:moi.geometryDatabase.getObjects().getConstructionLines().setProperty( "isTemporary", false );

Erase Helper Lines
script:var gd = moi.geometryDatabase; gd.removeObjects( gd.getObjects().getConstructionLines() );

works fine with the V 4 beta! ;)

Thank you for code. was mistakenly installing ConstructionLine3.zip which would seem no longer relevant to V4.

I took the code from here (should works also in the V3 (tested)
http://kyticka.webzdarma.cz/3d/moi/#KeepCLine