The drag and drop is for moving relationship’s breakpoints between start end end point.
Try to press CTRL and click anywhere on the relationship line. A new breakpoint will be created.
Now go over the new breakpoint with mouse cursor, and mouse cursor will change to arrow the like it chanes to arrow when you go over the end point.
when you drag the breakpoint, you can move it around.
If the end point can’t be detached and attached to new entity, then allowing to drag end point is a bug.
But still, when moving around breakpoint, both sibling lines are “dashed”. When moving around end points the line is solid no matter what kind of relationship it is.
Just released manual.chm has no information about detaching relationships, only info about breakpoints and formatting them.
I think it’s a bug. A bug that could be turned into new feature some day