This is important to know. I leave my half nut engaged and run the carriage back and forth, after disengaging the tool. I turn the power off when hitting the thread gutter. Then extract the tool, reverse the lathe to go back to the start and stop the spindle. Then set the tool depth and turn on the spindle forward.
There should be a way to resynchronize the spindle and carriage thread dial. It's going to be some modulo 127 or 100 ratio, but I haven't figured it out yet. I have an ELS and I'd like to do this. Have an encoder on the spindle and I can count steps for the lead screw. One of my round tuits that I'd like to figure out this year. I need to just work out the math - hopefully it will become obvious once I plot some stuff.