Sorry, moving a single edge of a mesh is currently not possible.
Once a comp is done, you have independent pieces of geometry. In your code above, the first comp separates the top from the extruded shape. The rest of the faces are discarded. The second comp separates the left edge of the top face from the rest of the face, and only the left edge remains. The edge is translated, but it is no longer connected to the rest of the mesh, and this probably isn't what you want. I'm guessing you want to move the edge but keep the connectivity to the rest of the mesh as it was after the extrude.
The only way to achieve something similar would be to figure out a different series of operations to make several independent pieces of geometry that when viewed as a whole resemble your original goal. For example, perhaps you could use roofShed() on your topbar face to get close to the end shape that you wanted.
