If I break a line using the "Split Entities" command,
choosing a random place in the middle, the 2 segments produced, are
inseparable, trimmed to each other. How can I detach the two
segments so that the shared end point in the middle is free on both
sides?
Edit: There is also a "detach segment on drag" toggle, by going to Tools>Sketch Settings>Detach segment on drag. This can sometimes be used to "pull points apart", but will not work on the end points of two colinear lines, as is in your example. I find it handy to have a shortcut for this toggle, so I can quickly turn it on and off again.