Gonzo : a runway is a runway , a taxi way a taxi way . Of course, providing you have a long displaced threshold you could use paint and shorten the runway , an could create a taxi way at the beginning of it , and displace the entrance of the runway clear of it to get proper height clearance. Then you need to change all the markings on the concrete and change the lights both on the new taxiway and remove those of the runway bit you closed , etc., and you do not have the original displaced threshold anymore as you cannot take off from a taxiway .The published data of your shorter new runway has to be changed as well everywhere and on the charts .
A NOTAM won't do it.