I'm using XL layout on a layout that was initially created in L and has no connectivity source.
Most of the layout work for this cell has been completed in L with no connectivity, so, I'm just using XL to create some nets within the already-completed-layout region (by assigning a net name in the Connectivity tab of the Edit Properties form for a shape in the completed area), and add some instance pins from the not-yet-laid-out region (using Connectivity -> Assign) to those nets, to get the flight lines and drag lines.
This is a big help, but, how can I remove an instance pin from a net, i.e. in case I screw up during the assignment?