Its already happened a couple of time to me. After creating a surface, I am not able to Trim Surface Edge. I made sure I was in Plan View. I’m using Version 5.60. When putting together the model, I was able trim the surface earlier, but I had to make multiple edits to my Side Slope command. When I click on the outside point, I don’t get coordinates in the command box.
If those outer edges are not defined by breaklines, then you will not be allowed to do trim edge. Way to trim will be to add a break line around the edge you want to trim or do a quick create surface edge boundary. You can then break that created boundary and add breaklines to those areas you want to trim. That breaklines you will want to join to the created surface edge which can then be used as a surface boundary for a quicker trim edge.