Generally speaking, I can't separate 2 lines joined by an end. No coincidence relationship is visible and therefore impossible for me to break their bond.
Where I have a big problem is in mechanically welded construction.
To separate these 2 lines I cut the end of one of the 2 lines but suddenly I lose all the parameters associated with this line: defined profile, orientation of the profile, insertion point.... And in a large frame it is quickly horror.
This solution does indeed allow the segments to be separated (only in 2D), but unfortunately the mechanically welded parameters of the displaced element are also lost.
The technique by generating a block by moving/lengthening/reducing the line to modified, then by popping this block does not lose the parameters.