From what I looked at, the delete_line function deletes lines connected to "input ports" and "output ports" of blocks. You can see the lines connected to the input/output ports blocks under:
>> A = get_param(gcb,'LineHandles')
In the generated structure A, you will see several fields like Inport, Outport, etc. The delete_line function looks at the inport and outport fields. For Simscape blocks, the lines show up under the LConn and RConn fields since the ports for Simscape blocks are technically not input ports and output ports, they are connection ports with no notion of input or output.
To delete the line connected to a Simscape block, you will need to get the Line Handle for the connection. Here's one way you can do this:
>> A = get_param(gcb,'LineHandles')
>> delete_line(A.LConn) % This will work if the line is connected to the left connection port of the Simscape block.
>> delete_line(A.RConn) % This will work if the line is connected to the right connection port of the Simscape block.
Hope this helps!
