Finally figured this out today. If you have a branching signal that you want to delete only a portion of, paste a simple block, like a sample delay, in the spot you want to snip the signal. Then delete the block. This will split the signal. If there is a better way to do this let me know.
Another workflow tip. If you want to swap out two versions of a subsystem with the same inputs and outputs, use Ctrl-x to cut the first one out. Then you can drag the other one in and all the signals will automatically reconnect. This saves time over disconnecting and re-connecting each signal manually. I commonly keep multiple variations of a subsystem commented out to test changes. Anyone have similar tips?