Is there a command like DupEdge but for curves?

Sometimes I want a part of curve but the curve may be in the group (the process can be cumbersome: remove it from group, copy in place, explode, remove the extra part, add it back into the group), or I want it to be untouched.

_ExtractSubCrv might do what you want…

ExtractSubCrv won’t work on grouped lines/arcs (nor on polylines), which is a issue to me. It can work on PolyCurves only.

Just _SubCrv with Copy=Yes should do what you want.